화학공학소재연구정보센터
Biochemical and Biophysical Research Communications, Vol.369, No.2, 327-332, 2008
Two conformational states of Ras GTPase exhibit differential GTP-binding kinetics
Previous P-31 NMR studies revealed that small GTPases H-Ras and K-Ras in complex with GTP assume two interconverting conformational states, state I and state 2. While state 2 corresponds to an active conformation, little is known about the function of state 1, an inactive conformation incapable of effector binding. To address the biochemical properties of state 1, we measured the P-31 NMR spectra of five Ras family small GTPases; H-Ras, M-Ras, Rap1A, Rap2A and Ra1A, and find that they exhibit distinctive state 2/state 1 populations with the ratios ranging from 0.072 for M-Ras to 16 for Rap2A. Further, we show that GTPases with higher populations of state I exhibit higher dissociation and association rate constants for GTP. These results imply that GTP loading to the nucleotide-free small GTPases preferentially yields state 1, which is subsequently converted to state 2, rendering the GTP-bound form functional. (c) 2008 Elsevier Inc. All rights reserved.