SynopsisThe first X-ray structure of the catalytic nucleotide-binding subunit A of the A 1 -ATPase has been determined at 2.55 Å resolution.Abstract H + -transporting ATP synthase is a multi-subunit enzyme involved in the production of ATP, which is essential molecule for living organisms as a source of energy. Archaeal A-type ATPase (A-ATPase) is thought to act as a functional ATP synthase in Archaea and is thought to have chimeric properties of F-ATPase and V-ATPase.From the previous structural studies of F-ATPase, it is indicated that the major nucleotide-binding subunits α and β consist of three domains. The catalytic nucleotide-binding subunit A of V/A-ATPase contains an insertion of about 90 residues, which is absent from the F 1 -β subunit. Here we describe the first X-ray structure of the catalytic nucleotide-binding subunit A of the A 1 -ATPase determined at 2.55 Å resolution. A 1 -ATPase subunit A from Pyrococcus horikoshii consists of four domains. A novel domain, including a part of this insertion, corresponds to the "knob-like structure" observed in electron microscopy of A 1 -ATPase. Based on the structure, it is highly likely that this inserted domain is related to the peripheral stalk common to the A-and V-ATPases. The arrangement of this inserted domain suggests that this region plays an important role in A-ATPase as well as in V-ATPase.

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H+ -transporting ATP synthase (H+ -ATPase) is a multi-subunit complex which acts to produce ATP molecules. The catalytic subunit A of the archaeal-type H+ -ATPase from Pyrococcus horikoshii OT3 was cloned, expressed in Escherichia coli, purified and crystallized by the hanging-drop vapour-diffusion method with MPD as a precipitant. X-ray intensity data were collected to 2.55 A resolution at beamline BL41XU of SPring-8. The crystals belong to the tetragonal space group P4(1)2(1)2 or P4(3)2(1)2, with unit-cell parameters a = b = 128.0, c = 104.7 A, and contain one molecule per asymmetric unit.

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