The N-terminal region of RadA, a MSCRAMM adhesin of the dominant symbiote Ruminococcus gnavus E1, binds human immunoglobulins and intestinal mucins

The present region is located immediately upstream of the rumA cluster involved in the Ruminococcin A-bacteriocin synthesis. It harbors three contiguous genes called radA, orfX and srtB. probably constituting independent transcriptional units.OrfX is 630 bp-long and could encode a conserved protein of unknown function exhibiting similarities with previously predicted proteins from Clostridium nexile DSM 1787 or Clostridium hathewayi DSM13479. srtB is 705 bp-long and codes for a putative protein exhibiting 41% identity with StrB sortases of Coprococcus comes ATCC27758 and Dorea formicigenerens ATCC27755. radA codes for a 1769 amino acids protein that exhibits strong homologies with different adhesion proteins homologous to the Cna-type adhesin of Staphylococcus aureus that belongs to the MSCRAMMs family. Characteristic structural motifs were found all over the deduced RadA-primary structure. An all-β bacterial Ig-like domain (from residues 38 to 128) was identified, able to interfere with a wide variety of extracellular matrix components.