Blüml K, Schnepp W, Schröder S, Beyermann M, Macias M, Oschkinat H, Lohse M J
Institut für Pharmakologie und Toxikologie der Universität Würzburg, Germany.
EMBO J. 1997 Aug 15;16(16):4908-15. doi: 10.1093/emboj/16.16.4908.
G-protein betagamma-subunits (G(betagamma)) are active transmembrane signalling components. Their function recently has been observed to be regulated by the cytosolic protein phosducin. We show here that a small fragment (amino acids 215-232) contained in the C-terminus of phosducin is sufficient for high-affinity interactions with G(betagamma). Corresponding peptides not only disrupt G(betagamma)-G(alpha) interactions, as defined by G(betagamma)-stimulated GTPase activity of alpha(o), but also other G(betagamma)-mediated functions. The NMR structure of a peptide encompassing this region shows a loop exposing the side chains of Glu223 and Tyr224, and peptides with a substitution of either of these amino acids show a complete loss of activity towards G(o). Mutation of this Tyr224 to Ala in full-length phosducin reduced the functional activity of phosducin to that of phosducin's isolated N-terminus, indicating the importance of this residue within the short, structurally defined C-terminal segment. This small peptide derived from phosducin, may represent a model of a G(betagamma) inhibitor, and illustrates the potential of small compounds to affect G(betagamma) functions.
G蛋白βγ亚基（Gβγ）是活跃的跨膜信号传导成分。最近观察到它们的功能受胞质蛋白磷光视蛋白调节。我们在此表明，磷光视蛋白C末端包含的一个小片段（氨基酸215 - 232）足以与Gβγ进行高亲和力相互作用。相应的肽不仅破坏Gβγ - Gα相互作用（如由Gβγ刺激的αo的GTP酶活性所定义），还破坏其他Gβγ介导的功能。包含该区域的肽的核磁共振结构显示出一个暴露Glu223和Tyr224侧链的环，并且替换这两种氨基酸中任何一种的肽对G o都完全丧失活性。在全长磷光视蛋白中将此Tyr224突变为Ala会使磷光视蛋白的功能活性降低至磷光视蛋白分离的N末端的活性水平，表明该残基在结构明确的短C末端片段中的重要性。这种源自磷光视蛋白的小肽可能代表一种Gβγ抑制剂模型，并说明了小分子化合物影响Gβγ功能的潜力。
