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Role of the switch II region in the conformational transition of activation of Ha-ras-p21

Published online by Cambridge University Press:  01 February 2000

JOSÉ FERNANDO DÍAZ ,
MARÍA MILAGROSA ESCALONA ,
STEVEN KUPPENS  and
YVES ENGELBORGHS
JOSÉ FERNANDO DÍAZ
Affiliation:
Laboratory of Biomolecular Dynamics, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001, Heverlee, Belgium Present address: Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Científicas, C/O Velazquez 144, 28006 Madrid, Spain.
MARÍA MILAGROSA ESCALONA
Affiliation:
Laboratory of Biomolecular Dynamics, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001, Heverlee, Belgium Present address: Servicio de Reumatología, Hospital General Universitario Gregorio Marañón, C/O Dr. Esquerdo 46, 28009, Madrid, Spain.
STEVEN KUPPENS
Affiliation:
Laboratory of Biomolecular Dynamics, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001, Heverlee, Belgium
YVES ENGELBORGHS
Affiliation:
Laboratory of Biomolecular Dynamics, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001, Heverlee, Belgium
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Abstract

The role of the switch II region in the conformational transition of activation of Ha-ras-p21 has been investigated by mutating residues predicted to act as hinges for the conformational transition of this loop (Ala59, Gly60, and Gly75) (Diaz JF, Wroblowski B, Schlitter J, Engelborghs Y, 1997, Proteins 28:434–451), as well as mutating the catalytic residue Gln61. The proposed mutations of the hinge residues decrease the rate of the conformational transition of activation as measured by the binding of BeF3− to the GDP-p21 complex. Also, the thermodynamic parameters of the binding reaction are altered by a factor between three and five, depending on the temperature. (Due to changes in activation and reaction enthalpies, partially compensated by entropy changes.) The control mutation Q61H in which only the catalytic residue is changed has only a limited effect on the kinetic rate constants of the conformational transition and on the thermodynamic parameters of the reaction.

The fact that mutations of the hinge residues of the switch II region affect both the binding of the phosphate analog and the conformational transition of activation indicates that the switch II is implicated both in the early and the late states of the transition.

Keywords

conformational changeG-proteinsmolecular dynamicsmolecular switchstopped flow
Type
Research Article
Information
Protein Science , Volume 9 , Issue 2 , February 2000 , pp. 361 - 368
Copyright
© 2000 The Protein Society

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