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Bovine heart mitochondrial F1-ATPase inhibited by AMP-PNP and ADP in the presence of thiophosphate.
Structural highlights
FunctionATPA_BOVIN Mitochondrial membrane ATP synthase (F(1)F(0) ATP synthase or Complex V) produces ATP from ADP in the presence of a proton gradient across the membrane which is generated by electron transport complexes of the respiratory chain. F-type ATPases consist of two structural domains, F(1) - containing the extramembraneous catalytic core, and F(0) - containing the membrane proton channel, linked together by a central stalk and a peripheral stalk. During catalysis, ATP synthesis in the catalytic domain of F(1) is coupled via a rotary mechanism of the central stalk subunits to proton translocation. Subunits alpha and beta form the catalytic core in F(1). Rotation of the central stalk against the surrounding alpha(3)beta(3) subunits leads to hydrolysis of ATP in three separate catalytic sites on the beta subunits. Subunit alpha does not bear the catalytic high-affinity ATP-binding sites (By similarity). Publication Abstract from PubMedThe rotation of the central stalk of F1-ATPase is driven by energy derived from the sequential binding of an ATP molecule to its three catalytic sites and the release of the products of hydrolysis. In human F1-ATPase, each 360 degrees rotation consists of three 120 degrees steps composed of substeps of about 65 degrees , 25 degrees , and 30 degrees , with intervening ATP binding, phosphate release, and catalytic dwells, respectively. The F1-ATPase inhibitor protein, IF1, halts the rotary cycle at the catalytic dwell. The human and bovine enzymes are essentially identical, and the structure of bovine F1-ATPase inhibited by IF1 represents the catalytic dwell state. Another structure, described here, of bovine F1-ATPase inhibited by an ATP analog and the phosphate analog, thiophosphate, represents the phosphate binding dwell. Thiophosphate is bound to a site in the alphaEbetaE-catalytic interface, whereas in F1-ATPase inhibited with IF1, the equivalent site is changed subtly and the enzyme is incapable of binding thiophosphate. These two structures provide a molecular mechanism of how phosphate release generates a rotary substep as follows. In the active enzyme, phosphate release from the betaE-subunit is accompanied by a rearrangement of the structure of its binding site that prevents released phosphate from rebinding. The associated extrusion of a loop in the betaE-subunit disrupts interactions in the alphaEbetaE-catalytic interface and opens it to its fullest extent. Other rearrangements disrupt interactions between the gamma-subunit and the C-terminal domain of the alphaE-subunit. To restore most of these interactions, and to make compensatory new ones, the gamma-subunit rotates through 25 degrees -30 degrees . How release of phosphate from mammalian F1-ATPase generates a rotary substep.,Bason JV, Montgomery MG, Leslie AG, Walker JE Proc Natl Acad Sci U S A. 2015 Apr 27. pii: 201506465. PMID:25918412[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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