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Updated: May 31, 2026

G Protein-selective GPCR Conformations Measured Using FRET Sensors in a Live Cell Suspension Fluorometer Assay
Published on: September 10, 2016
Interconversion of two GDP-bound conformations and their selection in an Arf-family small G protein
Hideyasu Okamura1, Masaki Nishikiori, Hongyu Xiang
1Division of Plant Sciences, National Institute of Agrobiological Sciences, 2-1-2, Kannondai, Tsukuba, Ibaraki 305-8602, Japan. hokamura@iae.kyoto-u.ac.jp
Abstract:
ADP-ribosylation factor (Arf) and other Arf-family small G proteins participate in many cellular functions via their characteristic GTP/GDP conformational cycles, during which a nucleotide(∗)Mg(2+)-binding site communicates with a remote N-terminal helix. However, the conformational interplay between the nucleotides, the helix, the protein core, and Mg(2+) has not been fully delineated. Herein, we report a study of the dynamics of an Arf-family protein, Arl8, under various conditions by means of NMR relaxation spectroscopy. The data indicated that, when GDP is bound, the protein core, which does not include the N-terminal helix, reversibly transition between an Arf-family GDP form and another conformation that resembles the Arf-family GTP form. Additionally, we found that the N-terminal helix and Mg(2+), respectively, stabilize the aforementioned former and latter conformations in a population-shift manner. Given the dynamics of the conformational changes, we can describe the Arl8 GTP/GDP cycle in terms of an energy diagram.
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