Molecular Modelling studies with Bowman Birk inhibitors
Institut für Physiologische Chemie und Pathobiochemie, Johannes Gutenberg University, Duesbergweg 6, 55099 Mainz, Germany
Protein homology molecular modelling combined with energy minimisations is used as a useful tool for obtaining insight into small structural perturbations as a result of amino acid replacements in the Bowman Birk inhibitor of serine proteases. This model protein built up from a relatively short amino acid chain of 71 residues contains a binary arrangement of a trypsin- and chymotrypsin-inhibitory subdomain and a rigid structural framework of seven disulfide bonds. We have performed molecular modelling studies with several homologues of BBI as an independent test for the validity of this approach followed by calculating models of different site directed mutants of the inhibitor. The models displayed only minor structural deviations with regards to the parent protein. These deviations were none the less extremely useful with regards to the irregularities in the variants monitored by comparative titration- and activity determination experiments in the two subdomains. These experimental and theoretical data will be used in order to derive a structural model of a coupled rather than independent folding of the two subdomains in the Bowman Birk inhibitors.