Effects of Carbon Source on Expression of F _o Genes and on the Stoichiometry of the c Subunit in the F ₁ F _o ATPase of Escherichia coli

Abstract

Expression of the genes for the membrane-bound Fosector of the Escherichia coli F1Foproton-translocating ATPase can respond to changes in metabolic conditions, and these changes are reflected in alterations in the subunit stoichiometry of the oligomeric Fo proton channel. Transcriptional and translational lacZ fusions to the promoter and to two Fo genes show that, during growth on the nonfermentable carbon source succinate, transcription of the operon and translation of uncB, encoding the a subunit of Fo, are higher than during growth on glucose. In contrast, translation of the uncE gene, encoding the c subunit of Fo, is higher during growth on glucose than during growth on succinate. Translation rates of both uncB anduncE change as culture density increases, but transcription rates do not. Quantitation of the c stoichiometry shows that more c subunits are assembled into the F1Fo ATPase in cells grown on glucose than in cells grown on succinate. E. coli therefore appears to have a mechanism for regulating the composition and, presumably, the function of the ATPase in response to metabolic circumstances.

Structural evidence for a constant c11 ring stoichiometry in the sodium F‐ATP synthase

“…These data are fully compatible with the recent finding that the stoichiometry of the subunit III cylinder within the ATP synthase of the green algae, C. reinhardtii, is not affected by the metabolic state of the cells [18]. However, such findings are difficult to reconcile with the proposed variation of c ring stoichiometries in E. coli, which are dependent on the expression level or the nutritional status of the cells [15].…”

“…The number of binding sites on the c ring determines the ATP to proton ⁄ Na + ratio, and therefore this stoichiometry is an important bioenergetic parameter for the cell. As the number of subunits can vary among species, the question was raised whether this stoichiometry could also vary within one species in order to adapt to specific energetic requirements of the cells [15]. This proposition seemed to be supported by an effect of the carbon source on the expression level of subunit c in Escherichia coli.…”

A tridecameric c ring of the adenosine triphosphate (ATP) synthase from the thermoalkaliphilic Bacillus sp. strain TA2.A1 facilitates ATP synthesis at low electrochemical proton potential

“…However, there is still an ongoing debate as to whether the c ring size can vary within a certain species. For example, the effect of the carbon source used for growth may affect the c-subunit stoichiometry (Schemidt et al, 1998). The subunit c from I. tartaricus when synthesized in E. coli is correctly assembled into c11 rings (Meier et al, 2005b), despite the preferred c10 stoichiometry of the native E. coli c ring Comparison of the resulting ring and subunit spectra prove the stoichiometry to be 11, 15 and 13 respectively.…”

New results about structure, function and regulation of the chloroplast ATP synthase (CF0CF1)

“…The chloroplast CF 0 consists of four different polypeptides in a stoichiometry of a 1 b 1 b% 1 c 12 (Fromme et al 1987). Variation in the number of copies of subunit c in the complex is discussed at least for the homologous subunit c in the E. coli ATP synthase (Schemidt et al 1998). Subunits c and a are directly involved in transmembrane proton transport.…”