Synthetic peptide inhibitors of complement serine proteases--I. Identification of functionally equivalent protease inhibitor sequences in serpins and inhibition of C1s and D.

Sequence homology comparisons between serum serine protease inhibitors led to the prediction that the C-terminal sequences are functionally equivalent and represent an essential protease binding domain. Inhibition of complement serine protease D cleavage of factor B and of C1s cleavage of C4 by synthetic peptides containing sequences from the C-termini of three serum serine protease inhibitors supports this prediction. These functionally equivalent peptides represent a new class of inhibitors of D and C1s as well as other serum serine proteases.