Abstract
Arf-family small G proteins participate in many cellular functions via their characteristic GTP/GDP conformational cycles, during which a nucleotide·Mg2+-binding site communicates with a remote N-terminal helix. We recently reported 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. In this review, I discuss the conformational interplay between the nucleotides, the helix, the protein core, and Mg2+.
