1</ref>.The molecular study of ATP synthase was initiated in 1960 when Efraim Racker and his colleagues reported thia isolation of soluable factor from beef heart mitochondria. ATP synthase produces ATP from adenosine diphosphate (ADP) and inorganic phosphate with the use of energy from a transmembrane proton-motive force generated by respiration or photosynthase[1].
Structure of ATP synthase
Strucutre of ATP synthases Image:1c17 dimor.jpgare basically similiar whatever the source. In their simplest form in prokaryotes, they contain eight different subunits, with stoichiometry α3β3γδεab2c10-14. The total molecular size is about 530kDa[2]. The enzyme consists of the extramembranous F1 catalytic domain linked by means of a central stalk to an intrinsic membrane domain called F0. In the atomic structure Of F1, the α and β subunits are arranged alternately around a coiled coil of two antiparallel α helices in the γ subunit [3].The catalytic sites are in the β subunits at the α/β subunit interface. The remainder of the γ subunit protrudes from the α3β3 assembly and can be cross linked to the polar loop region of the c subunits in F0. In mitochondria, the δ and ε subunits are associated with the γ subunit in the central stalk assembly, as are the bacterial and chloroplast ε subunits, the counterparts of mitochondrial δ. ATP-dependent rotation of γ and ε within an immobilized α3β3 complex from the thermophilic bacterium Bacillus PS3 has been observed directly[4].
High resolution structure analysis
The first atomic-level(2.8A) resolution structures by X-ray strucutures was of bovine mitochondrial F1 in 1994. The α and β subunits each had similiar three-domain structure, with an N-terminal β-barrel furthest away from the membrane surface, a central nucleotide-binding domain, and a C-terminal helical domain. Also, an NMR structure of isolated E. coli ε subunit is in good agreement with X-ray structure. The structure of the N-terminal domain of E. coli δ subunit consisting of residues 1 through 134 was solved also by NMR[5].
Mechanism of action
When the magnitude of △H is large, as in functionalmitochondrial, downhill proton flow through F0 causes rotation of the F0 rotor and hence rotation of the γε-subunits of F1. The rotary motion of the γ alternates the structure of the β-subunit so the ATP is synthesized[6].
Perspective
An emerging possibility of step-size mismatch between the F1 and F0 motors provides an opportunity to find a noval coupling mechanism of the two motors that will explain why the mismatch is good for the enzyme. Finally, one can even dream of using this, the world's tiniest motor, as an engine part in the fabrication of nano-machines. The marvel of ATP will continue.
Referances
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[1] ATP synthase-a marvellous
[2] Molecular Architecture of the rotary motor in ATP synthase
[3] The molecular mechanism of ATP
[4] Essentials for ATP synthesis by F1F0 ATP synthases
[5] ATP synthesis driven by proton tranport in
