tailieunhanh - Báo cáo khoa học: Local binding with globally distributed changes in a small protease inhibitor upon enzyme binding

Complexation of the small serine protease inhibitorSchistocerca gregaria chymotrypsin inhibitor (SGCI), a member of the pacifastin inhibitor family, with bovine chymotrypsin was followed by NMR spectroscopy. 1 H– 15 N correlation (HSQC) spectra of the inhibitor with increasing amounts of the enzyme reveal tight and specific binding in agreement with biochemical data. | ềFEBS Journal Local binding with globally distributed changes in a small protease inhibitor upon enzyme binding Zoltán Gáspári1 Borbala Szenthe2 Andras Patthy2 William M. Westler3 László Graf2 and Andras Perczel1 1 Institute of Chemistry Eotvos Lorand University Budapest Hungary 2 Institute of Biology Eotvos Lorand University Budapest Hungary 3 NationalMagnetic Resonance Facility at Madison University of Wisconsin-Madison MA USA Keywords enzyme-inhibitor complex internal dynamics NMR spectroscopy pacifastin inhibitor family SGCI Correspondence Andras Perczel Eotvos Lorand University Pazmany Peter setany 1 A Budapest 1117 Hungary E-mail perczel@ Received 2 January 2006 revised 6 February 2006 accepted 27 February 2006 doi Complexation of the small serine protease inhibitor Schistocerca gregaria chymotrypsin inhibitor SGCI a member of the pacifastin inhibitor family with bovine chymotrypsin was followed by NMR spectroscopy. 1H-15N correlation HSQC spectra of the inhibitor with increasing amounts of the enzyme reveal tight and specific binding in agreement with biochemical data. Unexpectedly and unparalleled among canonical serine protease inhibitors not only residues in the protease-binding loop of the inhibitor but also some segments of it located spatially far from the substrate-binding cleft of the enzyme were affected by complexation. However besides changes some of the dynamical features of the free inhibitor are retained in the complex. Comparison of the free and complexed inhibitor structures revealed that most but not all of the observed chemical shift changes can be attributed to minor structural transitions. We suggest that the classical scaffold binding loop model of canonical inhibitors might not be fully valid for the inhibitor family studied. In our view this feature allows for the emergence of both taxon-specific and nontaxon-specific inhibitors in this group of small proteins. Schistocerca gregaria .