PROSITE documentation PDOC52028Streptococcal M proteins C repeat and D repeats region profiles
M proteins belong to a family of fibrous streptococcal surface proteins that interact with the immune system of the host and represent major virulence factors due to their antiphagocytic activities. These antiphagocytic properties are explained by binding to a variety of different host proteins, with the most prominent one being fibrinogen. Another hypothesis relies on the M-protein-mediated formation of large bacterial aggregates, thereby inhibiting phagocytic engulfment. All M proteins share a common framework that includes a conserved signal peptide, a hypervariable amino terminus, a less variable central domain, and a highly conserved C-terminus. A number of repeat sequences (A, B, C and D repeats) follow the hypervariable region. Sequence conservation increases from the A repeats to D repeats. The size and number of the A and B repeats varies between different M proteins. Most M proteins do not possess any A repeats. The C repeats are present in all M proteins, although the number of repeat sequences varies from two (M6) to four (M12). The amino acid identity in the C repeat region increases from C1 to C3. The conserved repetitive C units are responsible for several biological activities of M and M-like proteins. The C units are involved in the binding of human serum albumin (HSA) to the M protein. Furthermore, the binding of complement factor H and streptococcal adherence to keratinocytes in human skin are mediated by the C units. Region D is composed of four seven-residue "quasirepeats" [1,2,3,4,5,6,7].
The M molecules exist as stable dimers the molecules are almost totally α-helical. A common periodicity in the placement of nonpolar or hydrophobic residues is responsible for maintaining the α-helical character of the proteins [1,2,3,4,5,6,7]. The streptococcal M proteins C repeat can adopt an α-helical structure (see <PDB:2KK9>) [8].
The profiles we developed cover respectively the entire streptococcal M proteins C repeat and D repeats region.
Last update:July 2023 / First entry.
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PROSITE methods (with tools and information) covered by this documentation:
| 1 | Authors | Hollingshead S.K. Fischetti V.A. Scott J.R. |
| Title | Complete nucleotide sequence of type 6 M protein of the group A Streptococcus. Repetitive structure and membrane anchor. | |
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| PubMed ID | 3511046 |
| 2 | Authors | Mouw A.R. Beachey E.H. Burdett V. |
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| PubMed ID | 3276665 | |
| DOI | 10.1128/jb.170.2.676-684.1988 |
| 3 | Authors | Fischetti V.A. |
| Title | Streptococcal M protein: molecular design and biological behavior. | |
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| DOI | 10.1128/CMR.2.3.285 |
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| Title | Two major classes in the M protein family in group A streptococci. | |
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| Title | C repeats of the streptococcal M1 protein achieve the human serum albumin binding ability by flanking regions which stabilize the coiled-coil conformation. | |
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| PubMed ID | 9201959 | |
| DOI | 10.1021/bi962991s |
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| Title | The streptococcal M protein: a highly versatile molecule. | |
| Source | Trends. Microbiol. 18:275-282(2010). | |
| PubMed ID | 20347595 | |
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| Source | mBio 4:E00629-E00612(2013). | |
| PubMed ID | 23481605 | |
| DOI | 10.1128/mBio.00629-12 |
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| Title | Anti-group A streptococcal vaccine epitope: structure, stability, and its ability to interact with HLA class II molecules. | |
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| PubMed ID | 21169359 | |
| DOI | 10.1074/jbc.M110.132118 |
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