title: Interconversion of two GDP-bound conformations and their selection in an Arf-family small G protein.
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.
authors: Division of Plant Sciences, National Institute of Agrobiological Sciences, 2-1-2, Kannondai, Tsukuba, Ibaraki 305-8602, Japan. hokamura@iae.kyoto-u.ac.jp
authors: Hideyasu
authors: H
authors: Okamura
authors: Masaki
authors: M
authors: Nishikiori
authors: Hongyu
authors: H
authors: Xiang
authors: Masayuki
authors: M
authors: Ishikawa
authors: Etsuko
authors: E
authors: Katoh
mesh_terms: D020727:ADP-Ribosylation Factors / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D002151:Calorimetry; D018360:Crystallography, X-Ray; D006153:Guanosine Diphosphate / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006801:Humans; D008274:Magnesium / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D009711:Nucleotides / Q000378:metabolism*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D013816:Thermodynamics
chemical_list: D009711:Nucleotides; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; C477339:ARL5B protein, human; D020727:ADP-Ribosylation Factors; D008274:Magnesium