COMPUTER-ANALYSIS OF THE BINDING REACTIONS LEADING TO A TRANSMEMBRANERECEPTOR-LINKED MULTIPROTEIN COMPLEX INVOLVED IN BACTERIAL CHEMOTAXIS

The chemotactic response of bacteria is mediated by complexes containi ng two molecules each of a transmembrane receptor and the intracellula r signaling proteins CheA and CheW. Mutants in which one or the other of the proteins of this complex are absent, inactive, or expressed at elevated amounts show altered chemotactic behavior and the phenotypes are difficult to interpret for some overexpression mutants. We have ex amined the possibility that these unexpected phenotypes might arise fr om the binding steps that lead to active complex formation. A limited genetic algorithm was used to search for sets of binding reactions and associated binding constants expected to give mutant phenotypes in ac cord with experimental data. Different sets of binding equilibria and different assumptions about the activity of particular receptor comple xes were tried. Computer analysis demonstrated that it is possible to obtain sets of binding equilibria consistent with the observed phenoty pes and provided a simple explanation for these phenotypes in terms of the distribution of active and inactive complexes formed under variou s conditions. Optimization methods of this kind offer a unique way to analyze reactions taking place inside living cells based on behavioral data.