5ik2
Caldalaklibacillus thermarum F1-ATPase (epsilon mutant)
Structural highlights
FunctionF5LA73_CALTT Produces ATP from ADP in the presence of a proton gradient across the membrane. The gamma chain is believed to be important in regulating ATPase activity and the flow of protons through the CF(0) complex.[ARBA:ARBA00003456][HAMAP-Rule:MF_00815] Publication Abstract from PubMedThe crystal structure has been determined of the F1-catalytic domain of the F-ATPase from Caldalkalibacillus thermarum, which hydrolyzes adenosine triphosphate (ATP) poorly. It is very similar to those of active mitochondrial and bacterial F1-ATPases. In the F-ATPase from Geobacillus stearothermophilus, conformational changes in the epsilon-subunit are influenced by intracellular ATP concentration and membrane potential. When ATP is plentiful, the epsilon-subunit assumes a "down" state, with an ATP molecule bound to its two C-terminal alpha-helices; when ATP is scarce, the alpha-helices are proposed to inhibit ATP hydrolysis by assuming an "up" state, where the alpha-helices, devoid of ATP, enter the alpha3beta3-catalytic region. However, in the Escherichia coli enzyme, there is no evidence that such ATP binding to the epsilon-subunit is mechanistically important for modulating the enzyme's hydrolytic activity. In the structure of the F1-ATPase from C. thermarum, ATP and a magnesium ion are bound to the alpha-helices in the down state. In a form with a mutated epsilon-subunit unable to bind ATP, the enzyme remains inactive and the epsilon-subunit is down. Therefore, neither the gamma-subunit nor the regulatory ATP bound to the epsilon-subunit is involved in the inhibitory mechanism of this particular enzyme. The structure of the alpha3beta3-catalytic domain is likewise closely similar to those of active F1-ATPases. However, although the betaE-catalytic site is in the usual "open" conformation, it is occupied by the unique combination of an ADP molecule with no magnesium ion and a phosphate ion. These bound hydrolytic products are likely to be the basis of inhibition of ATP hydrolysis. Regulation of the thermoalkaliphilic F1-ATPase from Caldalkalibacillus thermarum.,Ferguson SA, Cook GM, Montgomery MG, Leslie AG, Walker JE Proc Natl Acad Sci U S A. 2016 Sep 27;113(39):10860-5. doi:, 10.1073/pnas.1612035113. Epub 2016 Sep 12. PMID:27621435[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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