Identification of a t-rhamnopyranosyltransferase (RptA) involved in Corynebacterium glutamicum cell wall biosynthesis.

A bioinformatics approach identified a putative integral membrane protein, NCgl0543 in Corynebacterium glutamicum, with 13 predicted transmembrane domains and a glycosyltransferase motif (RXXDE), features that are common to the GT-C superfamily of glycosyltransferases. Deletion of C. glutamicum NCgl0543 resulted in a viable mutant. Further glycosyl linkage analyses of mAGP revealed a reduction of terminal-rhamnopyranosyl linked residues and as a result, a corresponding loss of branched 2,5-linked arabinofuranosyl residues, which was fully restored upon complementation of the deletion mutant by NCgl0543. As a result, we have now termed this previously uncharacterized open reading frame, rhamnopyranosyltransferase A (rptA). Furthermore, analysis of base-stable extractable lipids from C. glutamium revealed the presence of decaprenyl-monophosphorylrhamnose, a putative substrate for the cognate cell wall transferase.