Molecular Basis for the Coupling Ion Selectivity of F1F0 ATP Synthases: Probing the Liganding Groups for Na+ and Li+ in the c Subunit of the ATP Synthase from Propionigenium modestum

摘要: The conserved glutamate residue at position 65 of the Propionigenium modestum c subunit is directly involved in binding and translocation Na+ across membrane. site-specific introduction cQ32I cS66A substitutions putative vicinity to cE65 inhibited growth single-site mutants on succinate minimal agar, indicating that both amino acid residues are important for proper function oxidative phosphorylation system. This inhibition was abolished, however, if cF84L/cL87V double mutation additionally present P. subunit. newly constructed Escherichia coli strain MPC848732I, harboring cQ32I/cF84L/cL87V triple mutation, revealed a change coupling ion specificity from H+. ATP hydrolysis by this enzyme therefore not activated NaCl, ATP-driven H+ transport affected alkali salt. Both activities were influenced, LiCl. These data demonstrate loss site retention Li+ sites within mutant ATPase. In E. MPC848766A (cS66A/cF84L/cL87V), ATPase further restricted as exclusive ion. Therefore, neither nor stimulated activity, no observed. MPC32N (cQ32N) NaCl exhibited 5-fold higher Km but LiCl comparison parent strain. results requires liganding groups provided Q32, E65, S66. For coordination Li+, two partners, E65 S66, sufficient, mediated alone.