ATP synthase that lacks F0α-subunit -: Isolation, properties, and indication of F0b2-subunits as an anchor rail of a rotating c-ring

In a rotary motor F1F0-ATP synthase, F-0 works as a proton motor; the oligomer ring of F(0)c-subunits (c-ring) rotates relative to the F(0)ab(2) domain as protons pass through F-0 down the gradient. F(0)ab(2) must exert dual functions during rotation, that is, sliding the c-ring ( motor drive) while keeping the association with the c-ring ( anchor rail). Here we have isolated thermophilic F1F0(- a) which lacks F(0)a. F1F0(-a) has no proton transport activity, and F-0(-a) does not work as a proton channel. Interestingly, ATPase activity of F1F0(-a) is greatly suppressed, even though its F-1 sector is intact. Most likely, F(0)b(2) associates with the c-ring as an anchor rail in the intact F1F0; without F(0)a, this association prevents rotation of the c-ring ( and hence the gamma-subunit), which disables ATP hydrolysis at F-1. Functional F1F0 is easily reconstituted from purified F(0)a and F1F0(-a), and thus F(0)a can bind to its proper location on F1F0( - a) without a large rearrangement of other-subunits.