A Phylogenetic Approach for Assigning Function of Hypothetical Proteins in photorhabdus luminescens Subsp. laumondii TT01 Genome

摘要

Polyketides are larger family of structurally diverse natu- ral products with a broad range of biological activity. The occurrence of polyketide synthase gene family/cluster in bacteria is capable to synthesis the polyketides. In this study, sequence and structural similarities of some hypo- thetical proteins of Photorhabdus luminescens subsp. laumondii TTO1 analyzed to assign the functional rela- tionship with polyketide synthases (PKSs) using bioinformatics tools. Many hypothetical proteins of this organism have shown homologies to PKS family on which a significant homolog found to be located at genomic re- gion 2247626-2249476 bp in chromosome 1 carrying iden- tical function. On searching motif and domain, it showed a strong similarity to ketoacyl (KA) synthase I and then to acyl carrier protein. The ketosynthase- acyltransferasedidomain module 5 (2HG4) of Saccharopolyspora erythraea found as a good ortholog and the best template for modeling 3D structure from the sequences of hypothetical proteins. ProFunc and Castp servers used to annotate the structure-function relation- ship of protein models. The structural aspects at primary and secondary levels also showed a close resemblance to KA synthase. Phylogenetic analysis of this sequence and protein model ensured its function would be B-KA syn- thase showing the functional reliability like ketosynthase, and it has evolutionary relationship with soil bacteria. There was a horizontal gene transfer event to acquire this domain in Pluminescence genome. Consequently, an abun- dance of PKS gene in the genome of entomopathogenic bacteria will obviously helpful to protect its host nema- tode from other pathological pervasiveness.