Carb loading takes proteins on a ride

Christina Schäffer,Paul Messner

doi:10.1074/jbc.h118.002411

Abstract

Cytoplasmic protein O-glycosylation in bacteria is often required for protein maturation, but the dependence of protein export on carbohydrate modifications is less understood. In the current issue of JBC, Chen et al. describe the mechanism for posttranslational modification of a Streptococcus gordonii adhesin and its delivery to the membrane, leading to the first comprehensive model featuring the interplay of glycosyltransferases and the translocation system.

Highlights

Protein N- and O-glycosylation occurs in all domains of life (1, 2) and is frequently key to protein function
It has been speculated that the catalytic domain might be responsible for controlling GspB glycosylation, whereas the remainder might be required for glycoprotein transport (6)
The authors demonstrate that the adhesin is sequentially modified by three glycosyltransferases, with GftA/B adding an GlcNAc residue to Ser/Thr residues in serine-rich repeat (SRR), Nss transferring a glucose to the GlcNAc residues, and Gly adding further glucose residues

Summary

Introduction

Protein N- and O-glycosylation occurs in all domains of life (1, 2) and is frequently key to protein function. It has been speculated that the catalytic domain might be responsible for controlling GspB glycosylation, whereas the remainder might be required for glycoprotein transport (6).

Results

Conclusion