Mutations in the conserved proline 43 residue of the uncE protein (subunit c) of Escherichia coli F1F0-ATPase alter the coupling of F1 to F0
Year: 1989
Type: article
Abstract: The conserved Pro4' residue of the uncE protein (subunit c) of the Escherichia coli FIFO-ATPase was changed to Ser or Ala by oligonucleotide-directed mutagenesis, and the mutations were incorporated into the chromosome.The resultant mutant strains were capable of oxidative phosphorylation as indicated by their ability to grow on succinate and had growth yields on glucose that were 8 0 4 0 % of wild type.Membrane vesicles from the mutants were slightly less efficient than wild type vesicles in ATP-driven proton pumping as indicated by ATP-dependent quenching of quinacrine fluorescence.The decreased quenching response was not due to increased H+ leakiness of the mutant membranes or to loss of F1-ATPase activity from the membrane.These results indicate that the mutant FIFo-ATPases are defective in coupling ATP hydrolysis to H+ translocation.The membrane ATPase activity of the mutants was inhibited less by dicyclohexylcarbodiimide than that of wild type.The decrease in sensitivity to inhibition by dicyclohexylcarbodiimide was caused primarily by dissociation of the FI-ATPase from the mutant FO in the ATPase assay mixture.These results support the idea that Pro4', and neighboring conserved polar residues play an important role in the binding and functional coupling of FI to Fo.Although a Pro residue is found at position 43 in all species of subunit c studied, surprisingly, it is not absolutely essential to function.Proton-translocating FIFo-ATPases are found in the membranes of mitochondria, chloroplasts, and the plasma membranes of many bacteria.These reversible enzymes synthesize ATP by utilizing the energy stored in an electrochemical proton gradient (AbH+),' the Ab,+ being generated by respiratory or photosynthetic electron transport systems.ATPases
Source: Journal of Biological Chemistry
Authors: M J Miller, D Fraga, C R Paule, R H Fillingame
Institution: University of Wisconsin–Madison
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $3,430
OpenAlex ID: W1538643534