Function of the alpha subunit in mitochondrial ATP-synthase?
From: Uniprot 


  Mitochondrial membrane ATP synthase (F1F0 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, F1 - containing the extramembranous catalytic core, and F0 - containing the membrane proton channel, linked together by a central stalk and a peripheral stalk. During catalysis, ATP synthesis in the catalytic domain of F1 is coupled via a rotary mechanism of the central stalk subunits to proton translocation. Subunits alpha and beta form the catalytic core in F1. Rotation of the central stalk against the surrounding alpha3beta3 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. 




From: InterPro  


  There is a substrate-binding site on each of the alpha and beta subunits, those on the beta subunits being catalytic, while those on the alpha subunits are regulatory. The alpha-subunit contains a highly conserved adenine-specific non-catalytic nucleotide-binding domain, with a conserved amino acid sequence of Gly-X-X-X-X-Gly-Lys. The alpha and beta subunits form a cylinder that is attached to the central stalk. The alpha/beta subunits undergo a sequence of conformational changes leading to the formation of ATP from ADP, which are induced by the rotation of the gamma subunit, itself is driven by the movement of protons through the F0 complex C subunit [PMID: 12745923].


Sources: 


http://www.ebi.ac.uk/interpro/entry/IPR005294
http://www.uniprot.org/uniprot/P25705
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3278611/
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1679692/