title: E. coli F1-ATPase interacts with a membrane protein component of a proton channel.
abstract: The ATP synthases of bacteria, mitochondria and chloroplasts, which use the energy of a transmembrane proton gradient to power the synthesis of ATP, consist of an integral membrane component F0--thought to contain a proton channel--and a catalytic component, F1. To help investigate the way F0 and F1 are coupled, we have sequenced the b-subunit of the Escherichia coli F0, which seems to be the counterpart of a thermophilic bacteria F0 subunit thought to be essential for F1 binding. We report here that its sequence is remarkable, being hydrophobic around the N-terminus and highly charged in the remainder. We propose that the N-terminal segment lies in the membrane and the rest outside. The extramembranous section contains two adjacent stretches of 31 amino acids where the sequence is very similar: in the second of these stretches there is further internal homology. These duplicated stretches of the polypeptide probably fold into two alpha-helices which have many common features able to make contact with F1 subunits. Thus protein b occupies a central position in the enzyme, where it may be involved in proton translocation. It is possibly also important in biosynthetic assembly.
mesh_terms: D025181:ATP Synthetase Complexes; D000244:Adenosine Diphosphate / Q000235:genetics; D000251:Adenosine Triphosphatases / Q000032:analysis* / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D000595:Amino Acid Sequence; D004926:Escherichia coli / Q000201:enzymology; D006859:Hydrogen / Q000378:metabolism; D007473:Ion Channels / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D009097:Multienzyme Complexes / Q000235:genetics; D010770:Phosphotransferases / Q000235:genetics; D011487:Protein Conformation; D006180:Proton-Translocating ATPases
chemical_list: D007473:Ion Channels; D008565:Membrane Proteins; D009097:Multienzyme Complexes; D000244:Adenosine Diphosphate; D006859:Hydrogen; D010770:Phosphotransferases; D025181:ATP Synthetase Complexes; D000251:Adenosine Triphosphatases; D006180:Proton-Translocating ATPases