The importance of the second hairpin loop of cystatin C for proteinase binding. Characterization of the interaction of Trp-106 variants of the inhibitor with cysteine proteinases
The single Trp of human cystatin C, Trp-106, is located in the second hairpin loop of the proteinase binding surface. Substitution of this residue by Gly markedly altered the spectroscopic changes accompanying papain binding and reduced the affinity for papain, actinidin, and cathepsins B and H by 300-900-fold. The decrease in affinity indicated that the side chain of Trp-106 contributes a similar