Diversity, Abundance and Distribution of O-linked Glycosylation Pathway Enzymes in Prokaryotes-A Comparative Genomics Study

Abstract

In prokaryotes, the protein protein N- and O-glycosylation pathways (GlyPW) have been experimentally characterised in some of the organisms. Identifying GlyPWs in other prokaryotes is essential to understand the role of glycosylation. Herein we report a BLASTp and a hidden Markov model (HMM)-profile based comparative genomics approach to identify putative O-glycosylation enzymes in completely sequenced prokaryotic genomes using the experimentally characterized O-GlyPW enzymes as query sequences. Homologs for enzymes of all five categories viz., initiation, modification, extension, flippase and oligosaccharyltransferase are found in 128 organisms and no homolog is found for any of these in 52 organisms. A large number of organisms have homologs for all categories except oligosaccharyltransferases, which show high sequence diversity. Thus, O-GlyPW enzyme homologs are widely prevalent. Most of the 128 organisms are proteobacteria and more than half are pathogenic. The pattern of distribution of homologs indicates species- and strainspecific variations and acquisition of homologs by horizontal gene transfer.