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

Abstract

The chloroplast ATP synthase utilises the energy of a transmembrane electrochemical proton gradient to drive the synthesis of ATP from ADP and phosphate. This multi‐subunit thylakoid membrane‐bound enzyme consists of a proton channel, CF0, and an extrinsic catalytic sector, CF1. Stimulated by the elucidation of a three‐dimensional partial structure of the mitochondrial enzyme, substantial progress has been made to understand the catalytic mechanism and interesting hypotheses have been proposed about the molecular mechanism of energy coupling. The review discusses the present state of knowledge concerning the structure, molecular genetics, catalytic mechanism, energy coupling and regulation of this important enzyme involved in photophosphorylation.

Inactivation of the Chloroplast ATP Synthase γ Subunit Results in High Non-photochemical Fluorescence Quenching and Altered Nuclear Gene Expression in Arabidopsis thaliana

“…Three independent studies proved the rotation of the ␥ subunit relative to (␣␤) 3 during ATP hydrolysis in the isolated F 1 (5)(6)(7) and recently in isolated F 0 F 1 complexes (8).…”

“…The plastid ATP synthase complex consists of nine different subunits, four of them are localized in the membrane integral CF 0 subcomplex (a, b, bЈ, and c 14 ) which is responsible for proton translocation, and five subunits constitute the extrinsic CF 1 subcomplex (␣ 3 , ␤ 3 , ␥, ␦, and ⑀) which forms the catalytic entity (3,4). Three independent studies proved the rotation of the ␥ subunit relative to (␣␤) 3 during ATP hydrolysis in the isolated F 1 (5)(6)(7) and recently in isolated F 0 F 1 complexes (8).…”

14-3-3 protein is a regulator of the mitochondrial and chloroplast ATP synthase

“…In contrast to the mitochondrial enzyme, the chloroplast ATP synthase shows a complex regulation of catalytic activity (5,31). A high value of the proton motive force (⌬ Hϩ ) across the thylakoid membrane favors a high rate of ATP synthesis.…”

“…ATP is synthesized by the F type ATPase (ATP synthase), which is present in mitochondria, chloroplasts, and (photosynthetic) bacteria (1)(2)(3)(4). ATP synthases consist of an extrinsic catalytic F 1 complex that contains five different subunits (␣ 3 ␤ 3 ␥ 1 ␦ 1 1 ), and a proton pathway F o that is formed from a variable number of subunits, the stoichiometry of which is still under investigation (5,6). The crystal structure of the bovine ␣ 3 ␤ 3 ␥ 1 complex indicates that the ␣-and ␤-subunits are arranged alternately around the NH 2 -and COOH-terminal ␣-helices of the ␥-subunit.…”

“…⌬pH, thiol modulation, and nucleotide binding are all mechanisms used to avoid the dissipative cleavage of ATP (5). However, despite knowledge of these mechanisms, there remains an unexplained paradox in chloroplast energetics; namely, within whole isolated chloroplasts, the ATP synthase is rapidly deactivated in the dark, although broken chloroplasts (thylakoid particles) remain active for several hours after washing.…”