The proton conducting F0-part of bacterial ATP synthases

Role of the carboxyl‐terminal region of the PVP protein (F0I subunit) in the H+ conduction of F0F1 H+‐ATP synthase of bovine heart mitochondria

“…Because of its peripheral location at the M surface of the membrane this carboxylterminal tail cannot participate directly in transmembrane proton conduction. The present results show, however, that this segment of the PVP protein promotes proton conduction in F. possibly by favouring exchange of protons between the aqueous phase and the channel and/or by bringing the membrane-spanning protein segment [17,20] of the channel into the proper active configuration. This conclusion is also supported by the fact that removal of the carboxyl-terminal tail of the PVP protein induces loss of sensitivity of the FO proton 'channel to oligomycin.…”

Transmembrane topology of Escherichia coli H+‐ATPase (ATP synthase) subunit a

“…The catalytic sector F1 is present peripherally on the membrane and has five subunits, a, 15,7,8 and e, while the F0 sector in the membrane has three subunits, a, b and c, and functions as a proton channel [1][2][3][4]. The a subunit (271 amino acid residues), coded by the uncB gene, is extremely hydrophobic [5,6]. By analyzing a series of nonsense and missense mutants as well as site-directed mutants, it was found that the Arg-210, Glu-219, and His-245 residues are important for H + translocation as well as the binding of F1 [1][2][3][4], [7 10].…”

“…So far, five transmembrane models of subunit a, based on the results of hydropathy analysis [5,6,10], protease digestion [6], chemical cross-linking [11], location of chimeric fusion protein [12,13], and revertant analysis [14], have been proposed. However, there are many discrepancies in the orientations and identification of transmembrane segments among these models.…”

Oligomycin sensitivity‐conferring protein (OSCP) of beef heart mitochondria

“…The hydrophobic domain in the Nterminal sequence of OSCP may explain why this polypeptide remains bound to the membrane sector, while the corresponding subunit in the E. coli ATPase, i.e., the S-subunit, accompanies Fr when the latter is removed from the membrane. Analysis of the hydrophobicity profile of OSCP (not shown) shows a similarity to that of the E. coli b-subunit [24]. The b-subunit has a hydrophobic segment at the N-terminus which is embedded in the membrane, while the rest of the molecule is extremely hydrophilic and protrudes from the lipid bilayer.…”