Peterson Y K, Bernard M L, Ma H, Hazard S, Graber S G, Lanier S M
Departments of Pharmacology and Library and Informatics, Medical University of South Carolina, Charleston, South Carolina 29403, USA.
J Biol Chem. 2000 Oct 27;275(43):33193-6. doi: 10.1074/jbc.C000509200.
The G-protein regulatory (GPR) motif in AGS3 was recently identified as a region for protein binding to heterotrimeric G-protein alpha subunits. To define the properties of this approximately 20-amino acid motif, we designed a GPR consensus peptide and determined its influence on the activation state of G-protein and receptor coupling to G-protein. The GPR peptide sequence (28 amino acids) encompassed the consensus sequence defined by the four GPR motifs conserved in the family of AGS3 proteins. The GPR consensus peptide effectively prevented the binding of AGS3 to Gialpha1,2 in protein interaction assays, inhibited guanosine 5'-O-(3-thiotriphosphate) binding to Gialpha, and stabilized the GDP-bound conformation of Gialpha. The GPR peptide had little effect on nucleotide binding to Goalpha and brain G-protein indicating selective regulation of Gialpha. Thus, the GPR peptide functions as a guanine nucleotide dissociation inhibitor for Gialpha. The GPR consensus peptide also blocked receptor coupling to Gialphabetagamma indicating that although the AGS3-GPR peptide stabilized the GDP-bound conformation of Gialpha, this conformation of Gialpha(GDP) was not recognized by a G-protein coupled receptor. The AGS3-GPR motif presents an opportunity for selective control of Gialpha- and Gbetagamma-regulated effector systems, and the GPR motif allows for alternative modes of signal input to G-protein signaling systems.
AGS3中的G蛋白调节（GPR）基序最近被确定为蛋白质与异源三聚体G蛋白α亚基结合的区域。为了确定这个约20个氨基酸基序的特性，我们设计了一个GPR共有肽，并确定了它对G蛋白激活状态以及受体与G蛋白偶联的影响。GPR肽序列（28个氨基酸）包含了AGS3蛋白家族中四个保守的GPR基序所定义的共有序列。在蛋白质相互作用实验中，GPR共有肽有效地阻止了AGS3与Gialpha1,2的结合，抑制了鸟苷5'-O-(3-硫代三磷酸)与Gialpha的结合，并稳定了Gialpha的GDP结合构象。GPR肽对核苷酸与Goalpha和脑G蛋白的结合影响很小，表明其对Gialpha具有选择性调节作用。因此，GPR肽作为Gialpha的鸟嘌呤核苷酸解离抑制剂发挥作用。GPR共有肽还阻断了受体与Gialphabetagamma的偶联，这表明尽管AGS3-GPR肽稳定了Gialpha的GDP结合构象，但G蛋白偶联受体无法识别Gialpha(GDP)的这种构象。AGS3-GPR基序为选择性控制Gialpha和Gbetagamma调节的效应系统提供了机会，而GPR基序为G蛋白信号系统提供了信号输入的替代模式。
