A structurally distinct human mycoplasma protein that generically blocks antigen-antibody union
Grover RK, Zhu X, Nieusma T, Jones T, Boreo I, Boero I, MacLeod AS, Mark A, Niessen S, Kim HJ, Kong L, Assad-Garcia N, Kwon K, Chesi M, Smider VV, Salomon DR, Jelinek DF, Kyle RA, Pyles RB, Glass JI, Ward AB, Wilson IA, Lerner RA
We report the discovery of a broadly reactive antibody-binding protein (Protein M) from human mycoplasma. The crystal structure of the ectodomain of transmembrane Protein M differs from other known protein structures, as does its mechanism of antibody binding. Protein M binds with high affinity to all types of human and nonhuman immunoglobulin G, predominantly through attachment to the conserved portions of the variable region of the κ and λ light chains. Protein M blocks antibody-antigen union, likely because of its large C-terminal domain extending over the antibody-combining site, blocking entry to large antigens. Similar to the other immunoglobulin-binding proteins such as Protein A, Protein M as well as its orthologs in other Mycoplasma species could become invaluable reagents in the antibody field.