PDBsum entry 5hkk

Hydrolase

PDB id: 5hkk

Contents

Protein chains

(+ 0 more) 475 a.a.

(+ 0 more) 461 a.a.

284 a.a.

132 a.a.

Ligands

ADP ×12

GOL

PO4 ×2

ATP ×2

Metals

_MG ×12

Waters ×286

References listed in PDB file

Key reference

• Title: Regulation of the thermoalkaliphilic f1-Atpase from caldalkalibacillus thermarum.
• Authors: S.A.Ferguson, G.M.Cook, M.G.Montgomery, A.G.Leslie, J.E.Walker.
• Ref.: Proc Natl Acad Sci U S A, 2016, 113, 10860-10865. [DOI no: 10.1073/pnas.1612035113]
• PubMed id: 27621435

Abstract

The 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 ε-subunit are influenced by intracellular ATP concentration and membrane potential. When ATP is plentiful, the ε-subunit assumes a "down" state, with an ATP molecule bound to its two C-terminal α-helices; when ATP is scarce, the α-helices are proposed to inhibit ATP hydrolysis by assuming an "up" state, where the α-helices, devoid of ATP, enter the α3β3-catalytic region. However, in the Escherichia coli enzyme, there is no evidence that such ATP binding to the ε-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 α-helices in the down state. In a form with a mutated ε-subunit unable to bind ATP, the enzyme remains inactive and the ε-subunit is down. Therefore, neither the γ-subunit nor the regulatory ATP bound to the ε-subunit is involved in the inhibitory mechanism of this particular enzyme. The structure of the α3β3-catalytic domain is likewise closely similar to those of active F1-ATPases. However, although the βE-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.