Abstract
To characterize the interaction potential of the human vaginal isolate Lactobacillus plantarum CMPG5300, its genome was mined for genes encoding lectin-like proteins. cmpg5300.05_29 was identified as the gene encoding a putative mannose-binding lectin. Phenotypic analysis of a gene knock-out mutant of cmpg5300.05_29 showed that expression of this gene is important for auto-aggregation, adhesion to the vaginal epithelial cells, biofilm formation and binding to mannosylated glycans. Purification of the predicted lectin domain of Cmpg5300.05_29 and characterization of its sugar binding capacity confirmed the specificity of the lectin for high- mannose glycans. Therefore, we renamed Cmpg5300.05_29 as a mannose-specific lectin (Msl). The purified lectin domain of Msl could efficiently bind to HIV-1 glycoprotein gp120 and Candida albicans, and showed an inhibitory activity against biofilm formation of uropathogenic Escherichia coli, Staphylococcus aureus and Salmonella Typhimurium. Thus, using a combination of molecular lectin characterization and functional assays, we could show that lectin-sugar interactions play a key role in host and pathogen interactions of a prototype isolate of the vaginal Lactobacillus microbiota.
Highlights
Lectins are specific sugar-binding proteins or carbohydrate-binding agents (CBAs)
When we mined the genome sequence of L. plantarum CMPG5300 for putative lectin-encoding genes (Malik et al.11), the sortase-dependent, putative mannose-specific adhesin-encoding gene cmpg5300.05_29 of CMPG5300 was found to be located at the start and the end of a contig indicating the contig was circular, a plasmid
Inhibition of yeast agglutination with methyl-mannopyranoside, loss of mannan-binding capacity observed for the msl mutant, binding of the purified lectin domain to mannose-coated Sepharose beads, binding signal obtained with high-mannose N-glycans in the glycan array and competitive inhibition of Human Immunodeficiency Virus (HIV)-1 gp120-binding by a trimer of mannose, all validate the specificity of our L. plantarum lectin tomannoses
Summary
Lectins are specific sugar-binding proteins or carbohydrate-binding agents (CBAs). Because of the key role of sugar recognition in many physiological functions, they can be postulated to mediate crucial functions of the human microbiota, including colonization of the host and interaction with pathogens[10]. They are underexplored in functional microbiota studies. We investigated the lectin-sugar interaction potential of a vaginal microbiome isolate, Lactobacillus plantarum CMPG5300, for which we recently determined the genome sequence[11]. Genome mining of L. plantarum CMPG5300 resulted in the identification of cmpg5300.05_29 as the gene encoding a putative mannose-binding lectin
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