14 proton conducting subunits : 3 adenine nucleotide binding subunits
||John A. Raven Functional evolution of photochemical energy transformations in oxygen-producing organisms, Functional Plant Biology, 2009, 36, 505–515 p.508 left column 2nd paragraph
||Pogoryelov D, Reichen C, Klyszejko AL, Brunisholz R, Muller DJ, Dimroth P, Meier T. The oligomeric state of c rings from cyanobacterial F-ATP synthases varies from 13 to 15. J Bacteriol. 2007 Aug189(16):5895-902PubMed ID17545285
||Researchers isolated the c rings of F-ATP synthases from eight cyanobacterial strains belonging to four different taxonomic classes (Chroococcales, Nostocales, Oscillatoriales, and Gloeobacteria). These c rings showed different mobilities on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), probably reflecting their molecular masses. This supposition was validated with the previously characterized c(11), c(14), and c(15) rings, which migrated on SDS-PAGE in proportion to their molecular masses. Hence, the masses of the cyanobacterial c rings can conveniently be deduced from their electrophoretic mobilities and, together with the masses of the c monomers, allow the calculation of the c ring stoichiometries. The method is a simple and fast way to determine stoichiometries of SDS-stable c rings and hence a convenient means to unambiguously determine the ion-to-ATP ratio, a parameter reflecting the bioenergetic efficacy of F-ATP synthases.
||See table 1 in primary source. These rationalizations of the ecological occurrence of different c : b stoichiometries in the ATP synthetase must be considered in the context of thermodynamic measurements of the H+ : ATP ratio of 4.0 in the ATP synthetase from both Spinacia chloroplasts (c : ß = 14, theoretical H+ : ATP = 4.67) and Escherichia coli plasma membranes (c : ß = 10, theoretical H+ : ATP = 3.33) (Steigmiller et al. 2008). See BNID 105041,105043. Conversion of an electrochemical ion gradient into the universal energy currency ATP is performed by the enzyme F1Fo ATP synthase. The protein complex, which synthesizes ATP from ADP and phosphate, consists of two rotary motors, F1 and Fo, which are connected by a central and a peripheral stalk to exchange energy with each other. The oligomeric c-ring assemblies consist of an inner ring of a-helices surrounding a central phospholipid-containing cavity and an outer ring of a-helices that contacts the membrane phospholipids and/or subunit a. Each c subunit harbors an ion binding site in the middle of the membrane.