Physiological change in the ionophore‐portion of proton‐translocating ATPase in an uncoupled mutant of <i>Escherichia coli</i>

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The proton-tr~slocating ATPase complex (Fr-Fe) has essentially the same structure and function in chloroplasts, mitochondria and bacterial membranes (reviewed [l-3]). This complex is composed of two portions: a catalytic portion, Fr, and a proton pathway, Fe. Use of Escherichia coli as a source of Fl-Fe has the advantages that this organism is well characterized genetically, and that it is possible to study the physiological regulation of the complex in the bacteria. Differences have been found in the ionophoric properties of Fe from cells of the Fi mutant (NR 70, DW4) ofE: cuEi [4,5] grown aerobically and anaerobically. The sensitivity of strain RF7 to DCCD (dicyclohexylcarbodiimide) was shown ]6] to vary with growth conditions: when this strain is grown on a respiratory substrate its ATPase is resistant to DCCD, because of a mutational alteration in the DCCD binding protein in F,,, whereas when the cells are grown on glucose or glycerol the ATPase is significantly less resistant. Their results suggest that a functional change of the ATPase complex may occur when the growth conditions are varied. The purpose of the present communication is to provide further evidence that the Fe portion of the complex changes when the growth conditions are varied in aerobic culture. As shown below the proton permeability of membranes of the Fi mutant DL54 [7] varies with the physiological conditions under which the cells are grown. 2. Materials and methods

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