Arylformamidase Sequence & Homology

Our query sequence "Arylformamidase" is a putatuve thioesterase isloated from a Silicibacter sp. The sequence is 262 residues in length.

1. Method

Using the query sequence Target 13, pdb:2pbl "Arylformamidase", a BLAST search was performed on the bacterial sequence (File:Arylformamidase.txt) using a non-redundant database. The top scoring matches to an E-value of 3e-054, 35 sequences in total, were selected. Eukaryotic homologous sequences sequences were found using HOMOLOGENE. These were appended to the list and a multple sequece alignment was performed using CLUSTAL X.

The data output from the multiple sequence alignment was bootstrapped 1000 times and a phylogenetic tree was created using the neighbour-joining algorythm. The program FigTree was used to create the visual representation of this tree(Figure 1).

A similar BLAST search was performed using the human homologue to our query sequence. 126 of the top scoring matches were selected for a multiple sequence alignment. This was the minimum number of sequences which would also include the query sequence. The sequences were aligned, bootstrapped and a tree created as above. The tree revealed some questionable matches, joining humans with pufferfish for instance, which, whilst evolutionarily interesting poses more questions than answers.

Figure 1.

Unrooted phylogenetic tree of highest scoring results from a BLAST search of bacterial sequnces using a non-redundant database and homologous eukaryotic sequences sourced from HOMOLOGENE.

The final tree:

2. Results

Figure 1 shows that the query sequence "Arylformamidase" grouped with bacterial sequences, shown cloured in Red and Purple. 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. However, despite low bootstrap scores, the grouping does reliably separate prokaryotes from eukaryotes and the eukaryotes themsselves are clearly distinguished between yeasts and moulds (shown in Blue), plants (Green), invertebrates (Orange) and vertebrates (shown in Black).

The alignment revealed several conserved regions accross all species, thereby indicating a high level of conservation from Bacteria through Eukaryota. These included vertebrates, invertebrates, plants and single-celled eukaryotes (Figure 2).

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