Strep·to·coc·cus M an·ti·gen

the somatic antigen associated with virulence and type specificity of group A streptococci. It is antiphagocytic and there are more than 80 different types.

Synonym(s): M protein (1)

Farlex Partner Medical Dictionary © Farlex 2012

M protein

Haematology
Monoclonal IgM myeloma protein.

Microbiology
An alpha-helical fibrillary molecule on the surface of group A streptococcus, which has antiphagocytic properties and contributes to streptococcal virulences. Host antibodies against an N-terminal epitope confer protection against only one of the 80 distinct serotypes of group A streptococci (which differ according to antigenic variation in the M proteins). These serotypes share certain common structural motifs, having a coiled-coil rod in the centre and flanked by a C-terminal anchor constructed of a highly conserved hexapeptide (Leu-Pro-Ser-Thr-Gly-GluA; LPSTGE), which may be the idoneous antigen to be used for producing a vaccine, and an N-terminal anchor, the antigens of which are highly variable.

Physiology
A structural protein found in the M-band of striated muscle.

M protein

A constituent of the streptococcal cell wall which confers virulence on Type A streptococci by its anti-phagocytic action. M protein forms large and damaging aggregates with fibrinogen in blood and tissues and is the molecualar basis of the streptococcal toxic shock syndrome. The M protein-fibrinogen aggregates form powerful ligands for integrin receptors on polymorphs, thus activating these cells into the production of toxic metabolites and destructive enzymes.

Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005

M protein

Monoclonal or myeloma protein; IgM that is overproduced in Waldenstrom's macroglobulinemia and accumulates in the blood and urine.

Mentioned in: Waldenström's Macroglobulinemia

Patient discussion about M protein

Q. Well I’m a vegetarian and I might get anemia. How do I get Iron and protein without meat? My mom my take giant vitamin pills and eat nasty protein bars. It's not as bad killing animals though... Is their any way I can stay healthy? Also being a vegetarian has made me extremely under weight and I am probably going to get anemia if i don't get all my vitamins. HELP!

A. Any news Diana on this? I hope it has worked out for you.

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