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Biophys. J. BioFAST: First Published November 2, 2007. doi:10.1529/biophysj.107.114710
© 2007 by the Biophysical Society.

A more recent version of this article appeared on February 15, 2008.
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PROTEINS

Asymmetry of the GroEL-GroES Complex under Physiological Conditions as Revealed by Small-angle X-ray Scattering

Tomonao Inobe 1, Kazunobu Takahashi 1, Kosuke Maki 1, Sawako Enoki 1, Kiyoto Kamagata 1, Akio Kadooka 1, Munehito Arai 1 and Kunihiro Kuwajima 1*

1 University of Tokyo

* To whom correspondence should be addressed. E-mail: kuwajima{at}ims.ac.jp.

Submitted on June 9, 2007
Revised on July 12, 2007
Accepted on 10 October 2007


  Abstract
In spite of the well-known functional importance of GroEL-GroES complex formation during the chaperonin cycle, the stoichiometry of the complex has not been clarified. The complex can occur either as an asymmetric 1:1 GroEL-GroES complex or as a symmetric 1:2 GroEL-GroES complex, although it remains uncertain which type is predominant under physiological conditions. To resolve this question, we studied the structure of the GroEL-GroES complex under physiological conditions by small-angle X-ray scattering, which is a powerful technique to directly observe the structure of the protein complex in solution. We evaluated molecular structural parameters, the radius of gyration and the maximum dimension of the complex, from the X-ray scattering patterns under various nucleotide conditions (3 mM ADP, 3 mM ATP{gamma}S and 3 mM ATP in 10 mM MgCl2 and 100 mM KCl) at three different temperatures (10°C, 25°C, and 37°C). We then compared the experimentally observed scattering patterns with those calculated from the known X-ray crystallographic structures of the GroEL-GroES complex. The results clearly demonstrated that the asymmetric complex must be the major species stably present in solution under physiological conditions. On the other hand, in the presence of ATP (3 mM) and beryllium fluoride (10 mM NaF and 300 µM BeCl2), we observed the formation of a stable symmetric complex, suggesting the existence of a transiently formed symmetric complex during the chaperonin cycle.

Key Words: GroEL, chaperonin, molecular chaperone, protein folding, small-angle X-ray scattering




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T. Sameshima, T. Ueno, R. Iizuka, N. Ishii, N. Terada, K. Okabe, and T. Funatsu
Football- and Bullet-shaped GroEL-GroES Complexes Coexist during the Reaction Cycle
J. Biol. Chem., August 29, 2008; 283(35): 23765 - 23773.
[Abstract] [Full Text] [PDF]


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Copyright © 2007 by the Biophysical Society.