Mutations in the uncE gene affecting assembly of the c-subunit of the adenosine triphosphatase of Escherichia coli

Abstract

The amino acid substitutions in the mutant c-subunits of Escherichia coli F1F0-ATPase coded for by the uncE429, uncE408 and uncE463 alleles affect the incorporation of these proteins into the cell membrane. The DNA sequence of the uncE429 allele differed from normal in that a G leads to A base change occurred at nucleotide 68 of the uncE gene, resulting in glycine being replaced by aspartic acid at position 23 in the c-subunit. The uncE408 and uncE463 mutant DNA sequences were identical and differed from normal in that a C leads to T base change occurred at nucleotide 91 of the uncE gene, resulting in leucine being replaced by phenylalanine at position 31 in the c-subunit. An increased gene dosage of the uncE408 or uncE463 alleles resulted in the incorporation into the membranes of the mutant c-subunits. The results are discussed in terms of the 'Helical Hairpin Hypothesis' of Engelman & Steitz [(1981) Cell 23,411-422].

The proton conducting F0-part of bacterial ATP synthases

“…The mutant subunit e containing Phe-31 is forced into the membrane, and a functional FoF 1 originates, if the mutant gene is present at high copy number. This is not true for mutant subunit e containing Asp-23, i.e., a highly polar carboxyl group [111].…”

“…This is due to a substitution of Leu-31 by phenylanaline (une E 463) and Gly-23 by aspartic acid (une E429). [111]. The mutant subunit e containing Phe-31 is forced into the membrane, and a functional FoF 1 originates, if the mutant gene is present at high copy number.…”

“…The mutant allele shows a partial dominance over the wild-type allele. This suggests that this mutation does allow the assembly into F o [106,111].…”

The Subunit δ-Subunit b Domain of the Escherichia coli F1F0 ATPase

“…The mutation bG131D had previously been shown to allow assembly of the b subunit into the membrane but to prevent assembly of the whole F 1 F 0 ⅐ATPase complex (17). Replacement of Ala 128 by Asp is now known to disrupt dimer formation: b sol with the mutation A128D is a stable monomer (16).…”

Conserved Negative Charges in the Transmembrane Segments of Subunit K of the NADH:Ubiquinone Oxidoreductase Determine Its Dependence on YidC for Membrane Insertion

“…Attempts to elucidate the insertion requirements for this mutant in vitro were unsuccessful because of the proteinase K-resistant nature of the protein. 3 Substitution of a glycine for aspartate in TM1 of F o c results in a mutant form of the protein that is still dependent of YidC for insertion but that does not form an oligomeric ring structure as the wild type protein does (32,48). Thus the introduction of a negative charge into a TMS is tolerated by the YidC-only mode of insertion.…”