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  Topic: ATPase origins, Stuff pertinent to this question< Next Oldest | Next Newest >  

Posts: 97
Joined: May 2002

(Permalink) Posted: Oct. 15 2004,21:56   

FEBS Lett. 2004 Oct 8;576(1-2):1-4.

The evolution of A-, F-, and V-type ATP synthases and ATPases: reversals in function and changes in the H(+)/ATP coupling ratio.

Cross RL, Muller V.

Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, Syracuse, NY 13210, USA.

Members of the F(o)F(1), A(o)A(1) and V(o)V(1) family of ATP synthases and ATPases have undergone at least two reversals in primary function. The first was from a progenitor proton-pumping ATPase to a proton-driven ATP synthase. The second involved transforming the synthase back into a proton-pumping ATPase. As proposed earlier [FEBS Lett. 259 (1990) 227], these reversals required changes in the H(+)/ATP coupling ratio from an optimal value of about 2 for an ATPase function to about 4 for an ATP synthase function. The doubling of the ratio that occurred at the ATPase-to-Synthase transition was accomplished by duplicating the gene that encodes the nucleotide-binding catalytic subunits followed by loss of function in one of the genes. The halving of the ratio that occurred at the Synthase-to-ATPase transition was achieved by a duplication/fusion of the gene that encodes the proton-binding transporter subunits, followed by a loss of function in one half of the double-sized protein. These events allowed conservation of quaternary structure, while maintaining a sufficient driving force to sustain an adequate phosphorylation potential or electrochemical gradient. Here, we describe intermediate evolutionary steps and a fine-tuning of the H(+)/ATP coupling ratio to optimize synthase function in response to different environments. In addition, we propose a third reversal of function, from an ATPase back to an ATP synthase. In contrast to the first two reversals which required a partial loss in function, the change in coupling ratio required for the third reversal is explained by a gain in function.

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