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Large conformational changes of the epsilon subunit in the bacterial F1F0 ATP synthase provide a ratchet action to regulate this rotary motor enzyme.

Abstract：

:The F(1)F(0) ATP synthase is the smallest motor enzyme known. Previous studies had established that the central stalk, made of the gamma and epsilon subunits in the F(1) part and c subunit ring in the F(0) part, rotates relative to a stator composed of alpha(3)beta(3)deltaab(2) during ATP hydrolysis and synthesis. How this rotation is regulated has been less clear. Here, we show that the epsilon subunit plays a key role by acting as a switch of this motor. Two different arrangements of the epsilon subunit have been visualized recently. The first has been observed in beef heart mitochondrial F(1)-ATPase where the C-terminal portion is arranged as a two-alpha-helix hairpin structure that extends away from the alpha(3)beta(3) region, and toward the position of the c subunit ring in the intact F(1)F(0). The second arrangement was observed in a structure determination of a complex of the gamma and epsilon subunits of the Escherichia coli F(1)-ATPase. In this, the two C-terminal helices are apart and extend along the gamma to interact with the alpha and beta subunits in the intact complex. We have been able to trap these two arrangements by cross-linking after introducing appropriate Cys residues in E. coli F(1)F(0), confirming that both conformations of the epsilon subunit exist in the enzyme complex. With the C-terminal domain of epsilon toward the F(0), ATP hydrolysis is activated, but the enzyme is fully coupled in both ATP hydrolysis and synthesis. With the C-terminal domain toward the F(1) part, ATP hydrolysis is inhibited and yet the enzyme is fully functional in ATP synthesis; i.e., it works in one direction only. These results help explain the inhibitory action of the epsilon subunit in the F(1)F(0) complex and argue for a ratchet function of this subunit.

journal_name

Proc Natl Acad Sci U S A

journal_title

Proceedings of the National Academy of Sciences of the United States of America

authors

Tsunoda SP,Rodgers AJ,Aggeler R,Wilce MC,Yoshida M,Capaldi RA

doi

10.1073/pnas.111128098

keywords:

subject

Has Abstract

pub_date

2001-06-05 00:00:00

pages

6560-4

issue

eissn

0027-8424

issn

1091-6490

pii

111128098

journal_volume

pub_type

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Large conformational changes of the epsilon subunit in the bacterial F1F0 ATP synthase provide a ratchet action to regulate this rotary motor enzyme.