Crystallization of pilus proteins from gut-dwelling Ligilactobacillus ruminis

Adhesion to the host surface is the prerequisite for bacterial colonization, biofilm formation, and niche adaptation. The bacterial attachment is often facilitated through cell surface appendages called pili. In addition to adhesion, the pili also play a role in biofilm formation, immunomodulation, pathogenesis, and probiotic behaviours. The pili are usually composed of three protein subunits called tip, backbone, and basal pilins. These pilins are tethered to each other to form the pili through covalent links by an enzyme called sortase. Previously, We (Dr. Vengadesan Krishnan’s Laboratory of Structural Microbiology) characterized pilin subunits of pili from a well-known probiotic Lactobacillus rhamnosus GG and revealed the structural insights about the pilus formation and pili-mediated host interaction. We have now initiated a structural investigation of LrpCBA pilus components from Ligilactobacillus ruminis, a member of indigenous gut microbiota in humans and other animals. In addition to probiotic effects (immunomodulation, inhibition of pathogens, and maintenance of gut flora), the L. ruminis is an indispensable agent in the fermentation of foods and feed. In contrast to previously characterized L. rhamnosus GG pili (i.e., SpaCBA and SpaFED), the LrpCBA pili lack mucus-binding but show affinity to collagen and fibronectin. Hence, LrpCBA pili likely represent a third sortase-mediated pilus type in Lactobacillus species and differ from L. rhamnosus GG pili. We have now recombinantly produced all three LrpCBA pilus proteins (LrpA, LrpB, and LrpC) and obtained crystals for their structure determination. The knowledge from ongoing structural investigations will aid in understanding the pilus structure, function, and assembly process for promoting health and combating infections by targeting pili-mediated host interaction.

For more information: Prajapati A, Palva A, von Ossowski I, Krishnan V. (2021) LrpCBA pilus proteins of gut-dwelling Ligilactobacillus ruminis: crystallization and X-ray diffraction analysis, Acta Crystallogr F Struct Biol Commun. F77:238

https://doi.org/10.1107/S2053230X21007263

https://pubmed.ncbi.nlm.nih.gov/34341189/

LrpCBA pilus proteins @ActaCrystF @IUCr #LigilactobacillusRuminis #LrpCBAPili #Pilins https://t.co/f7FtBQxIuw pic.twitter.com/xVmkU8AEZj

— RCB (@unescorcb) August 2, 2021