Scientists have used mass spectrometry to provide evidence that the major secreted protein Msp1/p75 of the probiotic Lactobacillus rhamnosus GG is glycosylated.
The occurrence, biosynthesis and possible functions of glycoproteins have been increasingly documented for pathogens, however, glycoproteins are not usually described in probiotic bacteria.
Understanding the protein glycosylation could allow for a better understanding of specific glycan-mediated interactions of probiotics and also for glycoengineering in food-grade microbes.
This study has provided the first conclusive evidence of protein O-glycosylation in the probiotic L rhamnosus GG. In the study, Msp1 stained positive with periodic-acid Schiff staining, to be susceptible to chemical deglycosylation, and to bind with the mannose-specific Concanavalin A (ConA) lectin.
Mass spectrometry was then used to show that O-glycosylated and identified a glycopeptide TVETPSSA (amino acids 101-108) bearing hexoses presumably linked to the serine residues.
The examination of different cell extracts showed that Msp1 is a glycosylated protein in the supernatant, but not in the cell wall and cytosol fraction. This suggest that there is a link between glycosylation and secretion of this protein.
Posted by Fiona Griffiths