Protein M

Protein M (locus MG281) is an immunoglobulin-binding protein originally found on the cell surface of the human pathogenic bacterium Mycoplasma genitalium. It is presumably a universal antibody-binding protein, as it is known to be reactive against all antibody types tested so far. It is capable of preventing the antigen-antibody interaction due to its high binding affinity to any antibody. The Scripps Research Institute announced its discovery in 2014. It was detected from the bacterium while investigating its role in patients with a cancer, multiple myeloma.

Homologous proteins are found in other Mycoplasma bacteria. Mycoplasma pneumoniae, another human pathogen, has a homolog termed IbpM (locus MPN400).