Structure, function, and genetics of streptococcal M protein.
Streptococcal M protein is a coiled-coil fibrillar structure extending about 60 nm from the cell wall. From DNA sequencing of the M6 protein gene, it has been determined that the C-terminal end contains a membrane anchor and an adjacent cell wall stabilization domain, both of which are similar to C-terminal regions of surface proteins in other gram-positive organisms. Studies with monoclonal antibodies revealed that the C-terminal half of the protein is conserved among M proteins of different serotypes, whereas the N-terminal half varies. The M protein contains tandem repeats, which, through homologous recombination, are responsible for the observed size variation of the M proteins from different streptococcal strains. M protein size mutants occur in a laboratory-grown culture at a frequency of 1/2,000 colony-forming units. DNA sequence analysis of the M gene in size mutants derived from a single strain suggests that sequence changes which result from homologous recombination may play a role in the antigenic variation of M protein.
Fischetti
V A
VA
Rockefeller University, New York, New York 10021.
Jones
K F
KF
Hollingshead
S K
SK
Scott
J R
JR
D000940:Antigenic Variation; D000942:Antigens, Bacterial / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000032:analysis* / Q000235:genetics / Q000276:immunology; D002352:Carrier Proteins; D004269:DNA, Bacterial / Q000235:genetics; D011487:Protein Conformation; D013297:Streptococcus pyogenes
D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004269:DNA, Bacterial; C014689:streptococcal M protein