Three genes coding for subunits of the membrane sector (F0) of the Escherichia coli adenosine triphosphatase complex

Abstract

Two mutant unc alleles, unc-469 and unc-476, have been characterized as affecting a previously undescribed gene, designated uncF. The uncF gene is part of the unc operon (with the gene order being uncBFEAGDC), although some uncertainty remains as to the relative order of the uncF and uncE genes. Mutant strains carrying the uncF469 or uncF476 allele lack the 18,000-molecular-weight component of the F0 sector of the adenosine triphosphatase in the cell membrane but retain the dicyclohexylcarbodiimide-binding protein (molecular weight, 8,400). Conversely, strains carrying mutations in the uncE gene lack the dicyclohexylcarbodiimide-binding protein but retain the 18,000-molecular-weight protein in the cell membrane. Strains carrying mutations in the uncB gene have both the 18,000-molecular-weight protein and the dicyclohexylcarbodiimide-binding protein present in the cell membranes. The three proteins of the F0 portion of the adenosine triphosphatase, viz., 24,000, 18,000, and 8,400 molecular weights, became membrane associated after in vitro transcription-translation with plasmid pAN51 as template. Plasmids carrying deletions which affected the UncBFE region were isolated from plasmid pAN51 and characterized genetically. A comparison of the genes that were absent from the various deletion plasmids with the membrane-associated products formed after in vitro transcription-translation indicated that the uncB gene coded for the 24,000-molecular-weight protein and that the gene order was probably uncBFE. A correlation between length of deoxyribonucleic acid, genes present, and their products is presented in relation to plasmid pAN51.

Assembly of the adenosine triphosphatase complex in Escherichia coli: assembly of F0 is dependent on the formation of specific F1 subunits

“…There is some disagreement about the molecular weights of the Fo subunits of E. coli. However, those proposed by Foster and Fillingame (13) of 24,000, 19,000, and 8,400 agree well with the results of experiments with the cloned unc operon of E. coli in an in vitro transcription-translation system (7). Similar molecular weights have also been obtained for Fo components of M. phlei (4).…”

“…ATPase ASSEMBLY 37 VOL. 148, 1981 the uncF gene described so far resulted in the mutant protein not being incorporated into the membrane (7). A low level of both a-and fsubunits of F1 ATPase are membrane bound in uncF mutants, but no y-, 8-, or c-subunit could be detected (Fig.…”

“…6). Strains carrying the uncE429, uncE408, or uncE463 mutant allele do not incorporate the mutant dicyclohexylcarbodiimide-binding proteins into their membranes (7). However, such membranes were similar to membranes from uncF mutants in that a low level of both aand fl-subunits of F1 ATPase were bound and no -y-, 8-, or c-subunit was present (data not shown).…”

“…We assume that it is this component, coded for by the uncB gene (7), that is providing the binding site for the fl-subunit. The direct test of this assumption was not possible, since the only Mu-induced mutant available, strain AN887 (18), with a polar mutation affecting the entire unc operon, appeared to have the Mu Phage inserted in the region of the promoter, enabling the formation of a low level of the unc ylcarbodiimide-binding protein (8K) was present in the membrane but was not necessarily part of the Fo complex until the stage indicated (see text).…”

An additional acidic residue in the membrane portion of the b-subunit of the energy-transducing adenosine triphosphatase of Escherichia coli affects both assembly and function

“…The genes forming the unc operon in Escherichia coli code for the components of the energy-transducing adenosine triphosphatase complex and map at about 84min on the E. coli chromosome (Bachmann, 1983). Genetic studies Downie et al, 1981) and DNA sequencing (Gay & Walker, 1981) have established that the unc operon consists of nine genes in the order uncIBEFHAGDC, the uncI gene being closest to the promoter. The protein coded for by the uncI gene does not appear to be a structural component of the F1FO-ATPase complex (Gay & Walker, 1981).…”