Researchers reveal the structure of a protein that helps bacteria aggregate
Serine-rich repeat proteins (SRRPs), which help bacteria attach to surfaces, have been structurally characterised in pathogenic bacteria but not in beneficial bacteria such as those present in the gut. Dr Nathalie Juge’s team at the Quadram Institute Bioscience has previously identified SRRP as a main adhesin in Lactobacillus reuteri strains from pigs and mice. Now, together with colleagues at the University of East Anglia, they have described the structure and activity of the binding region of L. reuteri SRRPs in a paper published in PNAS. Using the Macromolecular Crystallography beamlines (I03 and I04) at Diamond Light Source, they discovered that the structure of these proteins is unique among characterised SRRPs and is surprisingly similar to pectin degrading enzymes. Molecular simulations and binding experiments revealed a pH-dependent binding to pectin and to proteins from the epithelium known as mucins. Altogether, these findings shed light on the activity of a key protein in these bacteria and may help guide the development of more targeted probiotic interventions.