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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.
Insights
Bacterial surface proteins, like streptococcal M protein, share structural similarities with mammalian muscle proteins such as tropomyosin. This molecular resemblance may influence streptococcal pathogenicity.
Area of Science:
- Microbiology
- Molecular Biology
- Biochemistry
Background:
- Bacterial surface proteins play crucial roles in host-pathogen interactions.
- Mammalian muscle proteins exhibit complex structures essential for function.
Purpose of the Study:
- To investigate potential structural relationships between bacterial surface proteins and mammalian muscle proteins.
- To explore the implications of these similarities for bacterial pathogenicity.
Main Methods:
- Amino-terminal sequence analysis of streptococcal M protein and staphylococcal protein A.
- Comparison with sequences of rabbit skeletal muscle tropomyosin, actin, and myosin A1 light chain.
- Assessment of amino acid composition and physicochemical properties.
Main Results:
- Significant sequence similarities (up to 40% identity) were found between streptococcal M protein peptides and rabbit tropomyosin.
- A repeating hexapeptide in M protein was identical to a tropomyosin sequence.
- Staphylococcal protein A sequences correlated highly with rabbit actin and myosin A1 light chain.
Conclusions:
- A close structural relationship exists between mammalian muscle proteins and bacterial surface proteins.
- Direct evidence of molecular similarity between streptococcal M protein and tropomyosin suggests implications for streptococcal pathogenicity.