A role for the fibrinogen-binding regions of streptococcal M proteins in phagocytosis resistance.
All virulent group A streptococcal isolates bind fibrinogen, a property that is closely linked to expression of type-specific antiphagocytic surface molecules designated M proteins. Here we show that although the M proteins from two different strains, M1 and M5, both bind fibrinogen with high affinity, they interact with different regions in the ligand. Moreover, mapping experiments demonstrated that the fibrinogen-binding regions in the M1 and M5 proteins are quite dissimilar at the amino acid sequence level and that they bind to different regions in the plasma protein. In spite of these differences, the fibrinogen-binding regions of M1 and M5 could both be shown to contribute to streptococcal survival in human blood, providing evidence for the distinct function of a plasma protein interaction in bacterial pathogenesis.
Ringdahl
U
U
Institute of Laboratory Medicine, Lund University, S-223 62 Lund, Sweden.
Svensson
H G
HG
Kotarsky
H
H
Gustafsson
M
M
Weineisen
M
M
Sjöbring
U
U
D000595:Amino Acid Sequence; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics; D005340:Fibrinogen / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D010587:Phagocytosis; D020449:Repetitive Sequences, Amino Acid; D013291:Streptococcus / Q000502:physiology
D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; C014689:streptococcal M protein; D005340:Fibrinogen