A secondary C1s interaction site on C1-inhibitor is essential for formation of a stable enzyme-inhibitor complex.
This paper examines the location of a secondary binding site for C1s on C1-inhibitor (C1-inh) which is required for the formation of SDS-stable Cls-C1-inh complexes. We used a synthetic peptide (residues 448-459) corresponding to the distal hinge region of C1-inh. This peptide binds to C1s and C1s preincubated with the peptide cleaves C1-inh but does not form a stable C1s-C1-inh complex. Computer modelling of C1-inh shows that residues Q452, Q453 and F455 are surface-exposed and that the secondary binding site may also include residues H291 and F292 which are conserved in serpins.
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Department of Microbiology and Immunology, University of Leicester, UK.
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Whaley
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D000818:Animals; D001665:Binding Sites; D003172:Complement C1 / Q000737:chemistry / Q000378:metabolism*; D003174:Complement C1 Inactivator Proteins / Q000737:chemistry / Q000378:metabolism*; D003196:Computer Graphics; D006801:Humans; D008958:Models, Molecular; D010455:Peptides / Q000378:metabolism; D011487:Protein Conformation
D003172:Complement C1; D003174:Complement C1 Inactivator Proteins; D010455:Peptides