Denker B M, Tempst P, Neer E J
Renal Division, Brigham and Women's Hospital, Boston, MA.
Biochem J. 1991 Sep 1;278 ( Pt 2)(Pt 2):341-5. doi: 10.1042/bj2780341.
Mastoparan is a 14-amino-acid peptide that stimulates secretion from several cell types. Secretion can be partially blocked by pertussis toxin and may be mediated by guanine-nucleotide-binding proteins (G-proteins). Mastoparan can act directly on G-proteins, probably at the hormone receptor-binding site, to stimulate guanosine 5'-[gamma-thio]triphosphate binding and GTPase activities of pertussis-toxin substrates Go and Gi [Higashijima, Uzu, Nakajima & Ross (1988) J. Biol. Chem. 263, 6491-6494]. We now describe a nucleotidase from bovine brain that is not a known G-protein whose GTPase and ATPase activities are stimulated by mastoparan. This nucleotidase hydrolyses ATP faster than GTP, but has similar affinities for both (0.4 microM). Mastoparan maximally stimulates both ATPase and GTPase activities by about 8-fold after insertion of the protein into phospholipid vesicles, but does not affect the EC50 (concentration at which half the maximal effect is observed) for ATP and GTP. The EC50 for mastoparan stimulation of GTPase and ATPase is 6 and 12 microM respectively. The native molecular mass of the partially purified mastoparan-stimulated nucleotidase is 87 kDa. This nucleotidase may be another receptor-activated enzyme, and its identification may be useful for understanding mastoparan-stimulated processes.
蜂毒肽是一种由14个氨基酸组成的肽，可刺激多种细胞类型的分泌。百日咳毒素可部分阻断这种分泌，其可能由鸟嘌呤核苷酸结合蛋白（G蛋白）介导。蜂毒肽可能直接作用于G蛋白，可能是在激素受体结合位点，以刺激鸟苷5'-[γ-硫代]三磷酸与百日咳毒素底物Go和Gi的结合以及GTP酶活性[东岛、宇津、中岛和罗斯（1988年）《生物化学杂志》263卷，6491 - 6494页]。我们现在描述一种来自牛脑的核苷酸酶，它不是已知的G蛋白，其GTP酶和ATP酶活性受到蜂毒肽的刺激。这种核苷酸酶水解ATP的速度比GTP快，但对两者的亲和力相似（0.4微摩尔）。将该蛋白插入磷脂囊泡后，蜂毒肽可使ATP酶和GTP酶活性最大程度地提高约8倍，但不影响ATP和GTP的半最大效应浓度（EC50）。蜂毒肽刺激GTP酶和ATP酶的EC50分别为6微摩尔和12微摩尔。部分纯化的受蜂毒肽刺激的核苷酸酶的天然分子量为87 kDa。这种核苷酸酶可能是另一种受体激活酶，对其进行鉴定可能有助于理解蜂毒肽刺激的过程。
