the bacterium can effectively evade the immune system of the host. This makes the protein an ideal target for developing new drugs. Rajesh Grover estimated that the protein can bind to an average of 100,000,000 different kinds of antibodies circulating in human blood. Unlike functionally similar proteins such as Protein A, Protein G, and Protein L, which all contain small, multiple immunoglobulin domains, Protein M has a large domain of 360 amino acid residues that binds primarily to the variable light chain of the immunoglobulin, as well as a binding site called LRR-like motif. In addition, Protein M has a C-terminal domain with 115 amino acid residues that probably protrudes over the antibody binding site. It binds to an antibody at either κ or λ light chains using hydrogen bonds and salt bridges, from backbone atoms and conserved side chains, and some conserved van der Waals interactions with other nonconserved interactions. References Bacterial proteins Sexually transmitted diseases and infections Immune system