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Arginine‐induced conformational change in the c ‐ring/ a ‐subunit interface of ATP synthase
Author(s) -
Vorburger Thomas,
Ebneter Judith Zingg,
Wiedenmann Alexander,
Morger Damien,
Weber Gerald,
Diederichs Kay,
Dimroth Peter,
von Ballmoos Christoph
Publication year - 2008
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2008.06368.x
Subject(s) - protein subunit , atp synthase , stator , arginine , chemistry , conformational change , biophysics , ring (chemistry) , stereochemistry , crystallography , biochemistry , biology , physics , enzyme , amino acid , organic chemistry , quantum mechanics , gene
The rotational mechanism of ATP synthases requires a unique interface between the stator a subunit and the rotating c ‐ring to accommodate stability and smooth rotation simultaneously. The recently published c ‐ring crystal structure of the ATP synthase of Ilyobacter tartaricus represents the conformation in the absence of subunit a . However, in order to understand the dynamic structural processes during ion translocation, studies in the presence of subunit a are required. Here, by intersubunit Cys–Cys cross‐linking, the relative topography of the interacting helical faces of subunits a and c from the I. tartaricus ATP synthase has been mapped. According to these data, the essential stator arginine ( a R226) is located between the c ‐ring binding pocket and the cytoplasm. Furthermore, the spatially vicinal residues c T67C and c G68C in the isolated c ‐ring structure yielded largely asymmetric cross‐linking products with a N230C of subunit a , suggesting a small, but significant conformational change of binding‐site residues upon contact with subunit a . The conformational change was dependent on the positive charge of the stator arginine or the a R226H substitution. Energy‐minimization calculations revealed possible modes for the interaction between the stator arginine and the c ‐ring. These biochemical results and structural restraints support a model in which the stator arginine operates as a pendulum, moving in and out of the binding pocket as the c ‐ring rotates along the interface with subunit a . This mechanism allows efficient interaction between subunit a and the c‐ ring and simultaneously allows almost frictionless movement against each other.