Identification of a domain in human factor H and factor H-like protein-1 required for the interaction with streptococcal M proteins.
The plasma protein factor H (FH) inhibits the alternative pathway of complement activation. Previous work has shown that FH binds to group A streptococci and that the interaction does not interfere with the complement-inhibitory capacity of FH. In this work, we report a molecular analysis of this interaction. In absorption experiments with human plasma, M protein-expressing group A streptococci bound both FH and FH-like protein-1 (FHL-1), an active 42-kDa splice product of the FH-gene transcript comprising the first 7 of its 20 short consensus repeat (SCR) domains. rFHL-1 also bound to M protein-expressing streptococci, but rFH fragments containing SCR 1-5 or SCR 1-6 did not. rFHL-1 bound to purified M5 protein with an affinity that was higher than the value calculated for the interaction between FH and M5 protein. The binding of radiolabeled rFHL-1 to immobilized M5 was blocked completely by unlabeled rFHL-1, but was inhibited only partially by SCR 1-6, emphasizing the importance of SCR 7 for the interaction. In experiments with the FH-related proteins FHR-3 and FHR-4, only the former bound to M protein-expressing streptococci, again pointing to an involvement of SCR 7, since FHR-3, but not FHR-4, contains a domain that is similar to SCR 7. Finally, the interaction between rFHL-1 and purified M5 protein was inhibited by heparin, which binds FH via SCR 7. Together, these data indicate that the interaction between streptococcal M proteins and FH or FHL-1 requires SCR 7.
Kotarsky
H
H
Department of Medical Microbiology, Lund University, Sweden.
Hellwage
J
J
Johnsson
E
E
Skerka
C
C
Svensson
H G
HG
Lindahl
G
G
Sjöbring
U
U
Zipfel
P F
PF
D000042:Absorption / Q000276:immunology; D000595:Amino Acid Sequence; D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000097:blood / Q000302:isolation & purification / Q000378:metabolism*; D001665:Binding Sites; D001798:Blood Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins; D017242:Complement Factor H / Q000378:metabolism*; D016384:Consensus Sequence / Q000235:genetics / Q000276:immunology; D006493:Heparin / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D010949:Plasma / Q000378:metabolism / Q000382:microbiology; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism; D013297:Streptococcus pyogenes / Q000276:immunology* / Q000378:metabolism
D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D001798:Blood Proteins; C493495:CFH protein, human; D002352:Carrier Proteins; D010446:Peptide Fragments; D011994:Recombinant Proteins; C100631:factor H-related protein 1; C014689:streptococcal M protein; D017242:Complement Factor H; D006493:Heparin