Circumstantial evidence for cytochrome b1 involvement in the functioning of lac-permease in respiring Escherichia coli.
The structure of the haem-binding site of cytochrome b1 and particularly the fact that the two protein ligands of the haem are methionines could explain a correlation found between loss of lac-permease activity and replacement of methionine by norleucine in the protein of aerobically respiring E. coli. If cytochrome b1 is essential for lac-permease mediated transport in whole bacteria as this correlation suggests, translocation of substrate by this permease must be coupled to electron transport. Such a dependence would invalidate the chemiosmotic interpretation of lactose transport in E. coli in its present form and would be in variance with the coupling-by-energy theories of lactose transport that exempted translocation from dependence on energy yielding processes.
Yariv
J
J
Laboratorie de Cristallographie et Physique Cristalline, Université de Bordeaux I, Talence, France.
D001426:Bacterial Proteins; D001693:Biological Transport, Active; D003573:Cytochrome b Group / Q000378:metabolism*; D004789:Enzyme Activation; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins; D005293:Ferritins / Q000378:metabolism*; D007785:Lactose / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D008715:Methionine / Q000378:metabolism; D009004:Monosaccharide Transport Proteins; D010101:Oxygen Consumption; D027981:Symporters
D001426:Bacterial Proteins; D003573:Cytochrome b Group; D029968:Escherichia coli Proteins; C050221:LacY protein, E coli; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D027981:Symporters; D005293:Ferritins; C018032:bacterioferritin; C021499:lactose permease; D008715:Methionine; D007785:Lactose