Method of modeling protein structure by the two-dimensional nuclear magnetic resonance spectro-scopy data; application to the proteinase inhibitor busi iia from bull seminal plasma

A new approach is suggested to model the spatial structure of protein molecules in solution based on combined use of the methods of theoretical conformational analysis and NMR spectroscopy data. At the first stage, special means are used to convert d connectivity information into the most probable values of dihedral angles. This allows search for possible spatial structures in the limited regions of the conformational space at further stages using the methods of the theoretical conformational analysis. The suggested approach was verified in reconstructing the spatial backbone structure of the fragment 17-57 of the proteinase inhibitor BUSI IIA from the bull seminal plasma. The structural model parameters are compared with the corresponding characteristics obtained from the X-ray analysis data for the homologic proteinase inhibitor from the Japanese quail ovomucoid. The suggested approach is shown to correctly reproduce both the general molecule topology and the conformations of individual amino acid residues.