Evidence by chemical modification that tryptophan-104 of the cysteine-proteinase inhibitor chicken cystatin is located in or near the proteinase-binding site. |
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Authors: | M Nycander I Bj?rk |
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Institution: | Department of Veterinary Medical Chemistry, Swedish University of Agricultural Sciences, Uppsala Biomedical Center, Sweden. |
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Abstract: | The single tryptophan residue Trp-104 of chicken cystatin was modified with a 2-hydroxy-5-nitrobenzyl group. The change of the absorption spectrum of this group on binding of the modified cystatin to papain indicated a decreased environmental polarity of the probe. The modified inhibitor had about a 10(5)-fold lower affinity for papain than had intact cystatin, this being due to a higher dissociation rate constant. These results show that Trp-104 of cystatin is located in or near the proteinase-binding site of the inhibitor, in agreement with a model proposed from computer docking Experiments. |
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