title: Amino acid sequence and physicochemical similarities between streptococcal M protein and mammalian tropomyosin.
abstract: The amino-terminal sequences of two peptides of type 24 streptococcal M protein show similarities with that of rabbit skeletal muscle tropomyosin, having up to 40% identical residues and probabilities of occurring by chance as low as P less than 10(-5). In addition, a hexapeptide (Glu-Ala-Glu-Lys-Ala-Ala) that is found five times in the M24 protein was shown to be identical to a sequence in tropomyosin. Similarities are also seen in the amino acid compositions and physicochemical properties of the two proteins. The amino-terminal sequences of peptides from another bacterial surface protein, staphylococcal protein A, are highly correlated with segments of two other myofibrillar proteins, rabbit actin (P less than 10(-7)) and rabbit myosin A1 light chain (P less than 10(-6)). The data presented suggest that a close structural relationship exists between mammalian muscle proteins and the biologically active surface proteins of staphylococci and streptococci. In addition, the correlation between sequences in M protein and tropomyosin represents direct evidence of a structural similarity at a molecular level between a streptococcal protein and a mammalian muscle component and may therefore prove relevant to the pathogenicity of the streptococcus.
mesh_terms: D000199:Actins; D000595:Amino Acid Sequence; D000954:Antigens, Surface; D001426:Bacterial Proteins / Q000276:immunology; D006358:Hot Temperature; D007526:Isoelectric Point; D008970:Molecular Weight; D009218:Myosins; D013297:Streptococcus pyogenes / Q000276:immunology*; D014335:Tropomyosin
chemical_list: D000199:Actins; D000954:Antigens, Surface; D001426:Bacterial Proteins; D014335:Tropomyosin; D009218:Myosins