Arylformamidase Results: Difference between revisions

From MDWiki
Jump to navigationJump to search
No edit summary
 
(15 intermediate revisions by 2 users not shown)
Line 3: Line 3:
'''2PBL Biological Structure'''
'''2PBL Biological Structure'''


The functional biological structure of arylformamidase is assumed by PDB to be a monomer (see figure 2) even though the 'whole' protein is shown to be interacting with chains A, B, C and D.  
The functional biological structure of 2PBL is assumed by PDB to be a monomer (see figure 3) even though the 'whole' protein is shown to be interacting with chains A, B, C and D.  
   
   
[[Image:ChainA1.PNG|centre|framed|'''Figure 2:''' ''2PBL exhibiting solely chain A. The unknown ligand (red) contains a ring composed of 9 oxygen molecules. The green sphere is a chloride ion. The protein backbone is coloured by conformation type: turn (blue), coil (pink), helix (green) and strand (purple). Image generated using PDB ProteinWorkshop 1.5'']]
[[Image:ChainA1.PNG|centre|framed|'''Figure 3:''' ''2PBL exhibiting solely chain A. The unknown ligand (red) contains a ring composed of 9 oxygen molecules. The green sphere is a chloride ion. The protein backbone is coloured by conformation type: turn (blue), coil (pink), helix (green) and strand (purple). Image generated using PDB ProteinWorkshop 1.5'']]


'''2PBL Interactions'''
'''2PBL Structural Similarity'''


STRING curated database showed that human arylformamidase significantly interacted with a number of proteins. However incidence of any of those proteins/genes to occur repeatedly in close neigbourhood in the genome is not significant. So is their co-occurence (i.e. absence of linked orthologous groups across species) and co-expression across the genome.
The DALI tool produces proteins that are structurally similar to the protein of interest. The search result showed similarities to be mostly carboxylesterases/hydrolases. The first significant hit from DALI was a carboxylesterase from a metagenomic Archeaon. The second significant hit was a carboxylesterase of ''Archaeoglobus fulgidus''. Analysis of 2PBL secondary structure similarity with the Archeal carboxylesterases showed conservation of the order of occurrence of different conformational types. For instance in all three proteins, the first conformation type is a helix and then three beta strands followed by a helix (see figures 4 & 5).


[[Image:Confidence_interaction_with_names.png|centre|framed|'''Figure 3:''' ''Interaction of human arylformamidase (AFMID) with other proteins from curated STRING database (significant score). There is no significant evidence for  Neighborhood in the genome, Gene fusions, Cooccurence across genomes, Co-Expression and experimental/biochemical data of such interactions.'']]
[[Image:PDBSum pblA.PNG|centre|framed|'''Figure 4:''' ''PDBSum output for arylformamidase. Image courtesy of PDBSUM.'']]  
 
The prokaryotic arylformamidase showed no significant interaction with any of the proteins listed below (score ~0.5)
 
[[Image:Examplec.jpg|centre|framed|'''Figure 4:''' ''Interaction of  2pbl from Silicibacter Sp. with other proteins'']]
 
TM1040_2226          ''Tryptophan 2,3-dioxygenase (279 aa)''
 
TM1040_2225          ''Kynureninase (396 aa)''
 
TM1040_2493          ''Succinic semialdehyde dehydrogenase (490 aa)''
 
TM1040_1862          ''Hypothetical protein (212 aa)''
 
TM1040_2491          ''Creatinase (402 aa'')
 
TM1040_2736          ''Transketolase, putative (794 aa)''
 
 
 
'''Structural similarity'''
 
The DALI tool produces proteins that are structurally similar to the protein of interest. The search result showed similarities to mostly carboxylesterases/hydrolases. Hence there is strong evidence that arylformamidase might also be a carboxylesterase.
[[Image:DALI RESULT.txt]]
 
 
The first significant hit from DALI was a metagenomic Archea carboxylesterase. The structure of carboxylesterase shows absence of ligands.
 
 
[[Image:ChainA 2c7b.PNG|centre|framed|'''Figure 5:''' ''Metagenomic Archea Carboxylesterase (Chain A ONLY).Note: Chain B not shown. From PDB ProteinWorkshop 1.5'']]   
[[Image:Carboxylase.txt]]
[http://www.rcsb.org/pdb/explore/explore.do?structureId=2C7B '''PDB''' ]
 
 
The second significant hit was the carboxylesterase of Archaeoglobus fulgidus. The ligand is present in this figure.
 
 
[[Image:ChainA 1jji.PNG|centre|framed|'''Figure 6:''' ''Archaeoglobus fulgidus Carboxylesterase exhibiting chain A only. From PDB ProteinWorkshop 1.5'']]
[[Image:Carboxylesterase (archaeon).txt]]
[http://www.rcsb.org/pdb/explore/explore.do?structureId=1JJI '''PDB''']
 
Both of the above Archaeal carboxylesterases' chains exist as monomers (from literature). Hence it is expected that our protein exists as a monomer but during crystallization it interacts with its chains.
 
 
'''Secondary structure analysis'''
 
 
Analysis of arylformamidase's secondary structure with the Archeal carboxylesterases showed the conservation of the order of occurrence of different conformational types. For instance in all three proteins, the first conformation type is a helix and then three beta strands followed by a helix and so on.
 
 
[[Image:PDBSum pblA.PNG|centre|framed|'''Figure 7:''' ''PDBSum output for arylformamidase. Image courtesy of PDBSUM.'']]  
[http://www.ebi.ac.uk/thornton-srv/databases/cgi-bin/pdbsum/GetPage.pl?pdbcode=2pbl&template=main.html PDBSUM]
[http://www.ebi.ac.uk/thornton-srv/databases/cgi-bin/pdbsum/GetPage.pl?pdbcode=2pbl&template=main.html PDBSUM]


[[Image:Pdbsums archeal.PNG|centre|framed|'''Figure 8:''' ''Archeon Carboxylesterase secondary structure. Image courtesy of PDBSUM.'']]   
[[Image:Pdbsums archeal.PNG|centre|framed|'''Figure 5:''' ''Archeon Carboxylesterase secondary structure. Image courtesy of PDBSUM.'']]   
 


'''The catalytic triad structure'''
'''The catalytic triad structure'''


A number of carboxylesterases perform their hydrolysis function using specific catalytic residues. The clustal alignment showed the conservation of the Archeal carboxylesterases catalytic triad in arylformamidase. The residues are Serine (Ser) 137, Glutamate (Glu) 215 and Histidine (His) 242. Residues Ser and His were fully conserved whereas E was semi-conserved. Using the human arylformamidase it was observed that Aspartate (asp) was used for eukaryotes instead of Glu, which is used for prokaryotes.
A number of carboxylesterases perform their hydrolysis function using specific catalytic residues. The ClustalW alignment showed conservation of the Archeal carboxylesterases catalytic triad in 2PBL. The residues are Serine (Ser) 137, Glutamate (Glu) 215 and Histidine (His) 242. Residues Ser and His were fully conserved whereas E was semi-conserved. Using the human arylformamidase it was observed that Aspartate (asp) was used for eukaryotes instead of Glu, which is used for prokaryotes.
 
[[Image:Untitled2.PNG|framed|centre|'''Figure 9:''' ''The catalytic triad. Unknown ligand (Blue) protruding from a surface groove. The residues are serine 136, Histidine 241 and Glutamate 214. '''Note:''' Actual residue numbers are n+1. Image generated using Pymol'' '']]
 


Other conserved/semi-conserved residues were annotated on the structure of arylformamidase. They are Asp 53, His 69, Gly 70, Gly 71, ''Tyr 72'', Trp 73, Gly 134, '''Ser 136''', Ala 137, Gly 138, ''His 140'', ''Ser 166'', ''Leu 168, Leu 171, Leu 174, '''Glu 214''''', '''His 241''', ''Val 244 and Leu 248'' The blue region in the below structure shows how they all are around the catalytic triad and the unknown ligand. This clearly shows their importance for the function of the protein as they have resisted mutations.
[[Image:Untitled2.PNG|framed|centre|'''Figure 6:''' ''The putative catalytic triad of 2PBL encompassing Serine 136, Histidine 241 and Glutamate 214. The unknown ligand (blue) protrudes from a surface groove. Image generated using Pymol.'']]


Regions of sequence were identified which were highly conserved between prokaryotic and eukaryotic species (see figure 7a). These residues were annotated on the structure of 2PBL (see figure 7b). The blue region in the figure below shows the clustering of conserved residues around the unknown ligand.


[[Image:Cat triad red.PNG|centre|framed|'''Figure 10:''' ''The conserved residues of arylformamidase. The blue region shows the residues conserved among species. It is mostly around the unknown ligand. The conserved residues were obtained from observing the clustal alignment.Image generated using Pymol'']]
'''Conserved''' - Asp53, His69, Gly70, Gly71, Trp73, Gly134, Ser136, Ala137, Gly138, His241.
   
'''Semi-conserved''' - Tyr72, His140, Ser166, Leu168, Leu171, Leu174, Glu214, Val244, Leu248.
  '''Catalytic triad''' - Ser136, Glu214, His241.


The distance between the catalytic triads can be seen in figure 11. Each of the residues are liked to a turn region. This catalytic triad as stated before is also conserved in the Metagenomic Archea Carboxylesterase (PDB ID 2C7B) and the Archaeoglobus fulgidus Carboxylesterase (PDB ID 1JJI). More so the catalytic triad in Archaeoglobus fulgidus Carboxylesterase is very close to the ligand (see figure 12).
[[Image:Alignment1.jpg|centre|framed|'''Figure 7a:''' ''The multiple sequence alignment performed between prokaryotic and eukaryotic sequences showing conserved regions.'']]


[[Image:Cat triad 1jji.PNG|framed|centre|'''Figure 12:''' ''The conserved catalytic triad in Archaeoglobus fulgidus Carboxylesterase (PDB ID 1JJI)'']]
[[Image:Cat triad red.PNG|centre|framed|'''Figure 7b:''' ''The conserved residues annotated on the structure of 2PBL. The blue region shows the residues conserved among species. It is mostly around the unknown ligand. The conserved residues were obtained from observing the clustal alignment. Image generated using Pymol.'']]


== Function ==  
== Function ==  


The most similar sequence from the BLAST search with functional information available was an arylformamidase isolated from the liver of ''Mus musculus'' (see figure ...). A functional analysis of this arylformamidase has been performed identifying a catalytic triad using site-directed mutagenesis (Pabarcus et al. 2007). Conservation of this catalytic triad with 2pbl was assessed (see figure...). Both residues Ser162 and His279 were found to be identical in relatively conserved regions of the alignment. However, Asp247 had undergone a semi-conservative substitution to glutamic acid. These residues correlated to Ser136, Glu214 and His241 of 2pbl which were subsequently located on the tertiary structure and determined to be sufficiently proximal to one another for catalysis (see figure...).
The most similar sequence from the BLAST search with functional information available was an arylformamidase isolated from the liver of ''Mus musculus'' (see figure 8). A functional analysis of this arylformamidase has been performed identifying a catalytic triad using site-directed mutagenesis (Pabarcus et al. 2007). Conservation of this catalytic triad with 2PBL was assessed using sequence homology (see figure 9). Both residues Ser162 and His279 were found to be identical in relatively conserved regions of the alignment. However, Asp247 had undergone a semi-conservative substitution to glutamic acid. These residues correlated to Ser136, Glu214 and His241 of 2PBL which were subsequently located on the tertiary structure and determined to be sufficiently proximal to one another for catalysis (see figure 10).


[[Image:2pblBLAST.png|centre|framed|'''Selected results of the BLAST search as performed by Sebastien.''']]
[[Image:2pblBLAST.png|centre|framed|'''Figure 8: ''Selected results of the BLAST search as performed by Sebastien.'']]


[[Image:arylformamidase_alignment.png|centre|framed|'''Figure ...:''' ''Conservation of the catalytic triad between Arylformamidase and 2PBL.'']]
[[Image:arylformamidase_alignment.png|centre|framed|'''Figure 9:''' ''Conservation of the catalytic triad between Arylformamidase and 2PBL.'']]


[[Image:CATALYTIC TRIAD 1.PNG|framed|centre|'''Figure ...:''' ''The putative catalytic triad identified through conservation with arylformamidase from ''Mus musculus''. Distances between the residues are shown. Note how each amino acid is linked to a turn region in the amino acid backbone. Generated using PDB ProteinWorkshop 1.5'']]
[[Image:CATALYTIC TRIAD 1.PNG|framed|centre|'''Figure 10:''' ''The putative catalytic triad identified through conservation with arylformamidase from ''Mus musculus''. Distances between the residues are shown. Note how each amino acid is linked to a turn region in the amino acid backbone. Generated using PDB ProteinWorkshop 1.5'']]


2PBL was found to share most structural similarity with a thermostable carboxylesterase from an uncultured archaeon (PDB ID: 2C7B; see figure ...). 2C7B shares a 16% sequence identity with 2PBL. From its structure, a catalytic triad has been identified with the residues Ser154, Asp251 and His281 (how?)(Byun, et al. 2007). To substantiate any functional similarity between 2PBL and 2C7B, conservation of the 2C7B catalytic triad was analysed (see figure ...). Both Ser154 and His281 matched, but Asp251 was not conserved at all, being replaced for a proline - a nonpolar, neutral amino acid. The sequence surrounding His281 was conserved to a lesser extent than in arylformamidase.
2PBL was found to share most structural similarity with a thermostable carboxylesterase from a metagenomic archaeon (PDB ID: 2C7B; see figure 11). 2C7B shares a 16% sequence identity with 2PBL. From its structure, a catalytic triad has been identified with the residues Ser154, Asp251 and His281 (Byun, et al. 2007). To substantiate any functional similarity between 2PBL and 2C7B, structural conservation of the 2C7B catalytic triad was analysed (see figure 12). Both Ser154 and His281 matched, but the aspartic acid had undergone a semi-conservative substitution to glutamic acid.  


[[Image:2c7b_alignment2.png|centre|framed|'''Figure ...:''' ''Conservation of the catalytic triad between 2cb7 and 2pbl.'']]
[[Image:DAL_HSLs.png|centre|framed|'''Figure 11''' ''Selected results of the DALI search performed by Basma encompassing structures of the HSL family of lipolytic enzymes as identified by Byun, et al. (2007).'']]


A number of proteins from the hormone-sensitive lipase (HSL) class of lipolytic enzymes as identified by Byun, et al. (2007) was found within top-scoring results of the DALI search (see figure...). To characterise sequence similarity, a ClustalW alignment of the amino acid sequences for these structures was performed (see figure ...).  
[[Image:2c7b_alignment2.png|centre|framed|'''Figure 12:''' ''Conservation of the catalytic triad between 2cb7 and 2pbl.'']]


[[Image:DAL_HSLs.png|centre|framed|'''Figure ...''' ''Selected results of the DALI search performed by Basma encompassing structures of the HSL family of lipolytic enzymes as identified by Byun, et al. (2007).'']]
A number of proteins from the hormone-sensitive lipase (HSL) class of lipolytic enzymes as identified by Byun, et al. (2007) was found within top-scoring results of the DALI search (see figure 11). To characterise sequence similarity, a multiple sequence alignment of the amino acid sequences for these structures was performed (see figure 13).  


[[Image:HSL_alignment.png|centre|framed|'''Figure ...:''' ''Alignment with members of the HSL class of lipolytic enzymes as identified by Byun, et al. (2007).'']]
[[Image:HSL_alignment.png|centre|framed|'''Figure 13:''' ''Alignment with members of the HSL class of lipolytic enzymes as identified by Byun, et al. (2007).'']]


== Sequence & Homology ==
== Sequence & Homology ==


Figure 1 shows that the query sequence "Arylformamidase" grouped with bacterial sequences, shown cloured in Blue. The bootstrap values reveal low confidence with many of the nodes occurring lower down on the phylogenetic tree revealing a possible explanation for certain closely related species to be grouped into separate clades. Interestingly, despite low bootstrap scores, the grouping reliably separates prokaryotes from eukaryotes and homologous eukaryotes include yeasts and moulds, plants, invertebrates and vertebrates.
The phylogenetic tree constructed using the multiple sequence alignment on 2PBL related sequences is shown in figure 14. The bootstrap values reveal low confidence with many of the nodes occurring lower down on the phylogenetic tree. This reveals a possible explanation for certain closely related species to be grouped into separate clades. Despite low bootstrap scores, the grouping reliably separates prokaryotes from eukaryotes. Interestingly, homologous eukaryotes include yeasts and moulds, plants, invertebrates and vertebrates.
 
[[Image:NewBOOT1000tree.png|centre|framed|'''Figure ...:''' ''Unrooted phylogenetic tree of highest scoring results from a BLASTP search of bacterial sequnces using a non-redundant database and homologous eukaryotic sequences sourced from NCBI HomoloGene. Branch lengths are related to phylogenetic distance and node numbers refer to Bootstrap values. On this tree "Arylformamidase" refers to the Silicibacter species from which our sequence originated. The colour coding distinguishes prokaryotic organisms shown in Blue, from eukaryote yeasts and moulds (shown in Green), plants (Dark Green), invertebrates (Orange) and vertebrates (shown in Red).'']]


To further elucidate the phylogeny of 2pbl, its human homologue, Arylformamidase, was queried in a BLAST search. The top scoring matches of bacterial homologues, present in Figure 1, were appended with top scoring matches of eukaryotic homologues. The human homologue, Arylformamidase, has a 26.28% sequence similarity. Despite this low score, multiple sequence alignment revealed that key regions were highly conserved between bacterial and eukayotic homologues.
[[Image:NewBOOT1000tree.png|centre|framed|'''Figure 14:''' ''Unrooted phylogenetic tree of highest scoring results from a BLASTP search of bacterial sequnces using a non-redundant database and homologous eukaryotic sequences sourced from NCBI HomoloGene. Branch lengths are related to phylogenetic distance and node numbers refer to Bootstrap values. On this tree "Arylformamidase" refers to the ''Silicibacter species'' from which 2PBL originated. The colour coding distinguishes prokaryotic organisms shown in blue, from eukaryote yeasts and moulds (shown in green), plants (dark green), invertebrates (orange) and vertebrates (shown in red).'']]


Figure 2 is largely consistent with traditional taxonomic groupings of organisms. Specifically, it reveals greater statistical confidence in the separation of prokaryotes (Blue and Green) and eukaryotes (invertebrates are shown in Orange; vertebrates are in Red).
To further elucidate the phylogeny of 2pbl, its human homologue, an arylformamidase, was queried in a BLAST search. The top scoring matches of bacterial homologues, present in figure 1, were appended with top scoring matches of eukaryotic homologues. The human homologue has a 26.28% sequence similarity. Despite this low score, multiple sequence alignment revealed that key regions were highly conserved between bacterial and eukaryotic homologues. This was demonstrated in a phylogenetic analysis of 2PBL and its human homologue which was largely consistent with traditional taxonomic groupings of organisms(see figure 15). Specifically, it reveals greater statistical confidence in the separation of prokaryotes and eukaryotes.


[[Image:BacterANDhomoTREE.jpg|centre|framed|'''Figure ...:''' ''Unrooted phylogenetic tree of highest scoring results from a BLASTP search of bacterial sequences and highest scoring results of a BLASTP search on a homologous human sequence. Branch lengths are related to phylogenetic distance and node numbers refer to Bootstrap values. On this tree "Arylformamidase" refers to the Silicibacter species from which our sequence originated. The colour coding distinguishes prokaryotes (Blue and Green) and eukaryotes (invertebrates are shown in Orange; vertebrates are in Red).'']]
[[Image:BacterANDhomoTREE.jpg|centre|framed|'''Figure 15:''' ''Unrooted phylogenetic tree of highest scoring results from a BLASTP search of bacterial sequences and highest scoring results of a BLASTP search on a homologous human sequence. Branch lengths are related to phylogenetic distance and node numbers refer to Bootstrap values. On this tree "Arylformamidase" refers to the ''Silicibacter'' species from which 2PBL originated. The colour coding distinguishes prokaryotes (blue and green) and eukaryotes (invertebrates are shown in orange; vertebrates are in red).'']]


In general, members of the same genus have been grouped together on these phylogenetic trees with some notable exceptions. For instance, Silicibacter, the species from which we derived our protein, occurs on disparate branches of the tree.
In general, members of the same genus have been grouped together on these phylogenetic trees with some notable exceptions. Notably, members of the ''Silicibacter'' clade occur on disparate branches of the tree.


[[Arylformamidase | Return to the main page...]]
[[Arylformamidase | Return to the main page...]]

Latest revision as of 03:28, 10 June 2008

Structure

2PBL Biological Structure

The functional biological structure of 2PBL is assumed by PDB to be a monomer (see figure 3) even though the 'whole' protein is shown to be interacting with chains A, B, C and D.

Figure 3: 2PBL exhibiting solely chain A. The unknown ligand (red) contains a ring composed of 9 oxygen molecules. The green sphere is a chloride ion. The protein backbone is coloured by conformation type: turn (blue), coil (pink), helix (green) and strand (purple). Image generated using PDB ProteinWorkshop 1.5

2PBL Structural Similarity

The DALI tool produces proteins that are structurally similar to the protein of interest. The search result showed similarities to be mostly carboxylesterases/hydrolases. The first significant hit from DALI was a carboxylesterase from a metagenomic Archeaon. The second significant hit was a carboxylesterase of Archaeoglobus fulgidus. Analysis of 2PBL secondary structure similarity with the Archeal carboxylesterases showed conservation of the order of occurrence of different conformational types. For instance in all three proteins, the first conformation type is a helix and then three beta strands followed by a helix (see figures 4 & 5).

Figure 4: PDBSum output for arylformamidase. Image courtesy of PDBSUM.

PDBSUM

Figure 5: Archeon Carboxylesterase secondary structure. Image courtesy of PDBSUM.

The catalytic triad structure

A number of carboxylesterases perform their hydrolysis function using specific catalytic residues. The ClustalW alignment showed conservation of the Archeal carboxylesterases catalytic triad in 2PBL. The residues are Serine (Ser) 137, Glutamate (Glu) 215 and Histidine (His) 242. Residues Ser and His were fully conserved whereas E was semi-conserved. Using the human arylformamidase it was observed that Aspartate (asp) was used for eukaryotes instead of Glu, which is used for prokaryotes.

Figure 6: The putative catalytic triad of 2PBL encompassing Serine 136, Histidine 241 and Glutamate 214. The unknown ligand (blue) protrudes from a surface groove. Image generated using Pymol.

Regions of sequence were identified which were highly conserved between prokaryotic and eukaryotic species (see figure 7a). These residues were annotated on the structure of 2PBL (see figure 7b). The blue region in the figure below shows the clustering of conserved residues around the unknown ligand.

Conserved - Asp53, His69, Gly70, Gly71, Trp73, Gly134, Ser136, Ala137, Gly138, His241.
Semi-conserved - Tyr72, His140, Ser166, Leu168, Leu171, Leu174, Glu214, Val244, Leu248.
Catalytic triad - Ser136, Glu214, His241.
Figure 7a: The multiple sequence alignment performed between prokaryotic and eukaryotic sequences showing conserved regions.
Figure 7b: The conserved residues annotated on the structure of 2PBL. The blue region shows the residues conserved among species. It is mostly around the unknown ligand. The conserved residues were obtained from observing the clustal alignment. Image generated using Pymol.

Function

The most similar sequence from the BLAST search with functional information available was an arylformamidase isolated from the liver of Mus musculus (see figure 8). A functional analysis of this arylformamidase has been performed identifying a catalytic triad using site-directed mutagenesis (Pabarcus et al. 2007). Conservation of this catalytic triad with 2PBL was assessed using sequence homology (see figure 9). Both residues Ser162 and His279 were found to be identical in relatively conserved regions of the alignment. However, Asp247 had undergone a semi-conservative substitution to glutamic acid. These residues correlated to Ser136, Glu214 and His241 of 2PBL which were subsequently located on the tertiary structure and determined to be sufficiently proximal to one another for catalysis (see figure 10).

Figure 8: Selected results of the BLAST search as performed by Sebastien.
Figure 9: Conservation of the catalytic triad between Arylformamidase and 2PBL.
Figure 10: The putative catalytic triad identified through conservation with arylformamidase from Mus musculus. Distances between the residues are shown. Note how each amino acid is linked to a turn region in the amino acid backbone. Generated using PDB ProteinWorkshop 1.5

2PBL was found to share most structural similarity with a thermostable carboxylesterase from a metagenomic archaeon (PDB ID: 2C7B; see figure 11). 2C7B shares a 16% sequence identity with 2PBL. From its structure, a catalytic triad has been identified with the residues Ser154, Asp251 and His281 (Byun, et al. 2007). To substantiate any functional similarity between 2PBL and 2C7B, structural conservation of the 2C7B catalytic triad was analysed (see figure 12). Both Ser154 and His281 matched, but the aspartic acid had undergone a semi-conservative substitution to glutamic acid.

Figure 11 Selected results of the DALI search performed by Basma encompassing structures of the HSL family of lipolytic enzymes as identified by Byun, et al. (2007).
Figure 12: Conservation of the catalytic triad between 2cb7 and 2pbl.

A number of proteins from the hormone-sensitive lipase (HSL) class of lipolytic enzymes as identified by Byun, et al. (2007) was found within top-scoring results of the DALI search (see figure 11). To characterise sequence similarity, a multiple sequence alignment of the amino acid sequences for these structures was performed (see figure 13).

Figure 13: Alignment with members of the HSL class of lipolytic enzymes as identified by Byun, et al. (2007).

Sequence & Homology

The phylogenetic tree constructed using the multiple sequence alignment on 2PBL related sequences is shown in figure 14. The bootstrap values reveal low confidence with many of the nodes occurring lower down on the phylogenetic tree. This reveals a possible explanation for certain closely related species to be grouped into separate clades. Despite low bootstrap scores, the grouping reliably separates prokaryotes from eukaryotes. Interestingly, homologous eukaryotes include yeasts and moulds, plants, invertebrates and vertebrates.

Figure 14: Unrooted phylogenetic tree of highest scoring results from a BLASTP search of bacterial sequnces using a non-redundant database and homologous eukaryotic sequences sourced from NCBI HomoloGene. Branch lengths are related to phylogenetic distance and node numbers refer to Bootstrap values. On this tree "Arylformamidase" refers to the Silicibacter species from which 2PBL originated. The colour coding distinguishes prokaryotic organisms shown in blue, from eukaryote yeasts and moulds (shown in green), plants (dark green), invertebrates (orange) and vertebrates (shown in red).

To further elucidate the phylogeny of 2pbl, its human homologue, an arylformamidase, was queried in a BLAST search. The top scoring matches of bacterial homologues, present in figure 1, were appended with top scoring matches of eukaryotic homologues. The human homologue has a 26.28% sequence similarity. Despite this low score, multiple sequence alignment revealed that key regions were highly conserved between bacterial and eukaryotic homologues. This was demonstrated in a phylogenetic analysis of 2PBL and its human homologue which was largely consistent with traditional taxonomic groupings of organisms(see figure 15). Specifically, it reveals greater statistical confidence in the separation of prokaryotes and eukaryotes.

Figure 15: Unrooted phylogenetic tree of highest scoring results from a BLASTP search of bacterial sequences and highest scoring results of a BLASTP search on a homologous human sequence. Branch lengths are related to phylogenetic distance and node numbers refer to Bootstrap values. On this tree "Arylformamidase" refers to the Silicibacter species from which 2PBL originated. The colour coding distinguishes prokaryotes (blue and green) and eukaryotes (invertebrates are shown in orange; vertebrates are in red).

In general, members of the same genus have been grouped together on these phylogenetic trees with some notable exceptions. Notably, members of the Silicibacter clade occur on disparate branches of the tree.

Return to the main page...