Fung B K, Griswold-Prenner I
Jules Stein Eye Institute, University of California School of Medicine, Los Angeles 90024.
Biochemistry. 1989 Apr 18;28(8):3133-7. doi: 10.1021/bi00434a003.
The cyclic GMP phosphodiesterase of retinal rods is composed of three distinct polypeptides: alpha (90 kDa), beta (86 kDa), and gamma (10 kDa). In this multimeric form, the enzyme is inhibited. Its activity is stimulated by the interaction with the GTP-bound form of the T alpha subunit of transducin and reversed upon the recombination of the inhibitory gamma subunit with the catalytic alpha beta subunit. We show here by a novel coimmunoprecipitation technique that the gamma subunit, but not the alpha beta subunit, forms a 1:1 complex with T alpha. The binding of gamma to T alpha is nucleotide-dependent and is facilitated by GTP gamma S or Gpp(NH)p. This study provides convincing evidence that the T alpha-GTP subunit of transducin stimulates phosphodiesterase activity by binding to gamma and physically carrying it away from alpha beta.
α（90 kDa）、β（86 kDa）和γ（10 kDa）。在这种多聚体形式下，该酶受到抑制。其活性通过与转导素Tα亚基的GTP结合形式相互作用而被刺激，并在抑制性γ亚基与催化性αβ亚基重新结合后逆转。我们在此通过一种新型的共免疫沉淀技术表明，γ亚基而非αβ亚基与Tα形成1:1复合物。γ与Tα的结合是核苷酸依赖性的，并且被GTPγS或Gpp(NH)p促进。这项研究提供了令人信服的证据，即转导素的Tα-GTP亚基通过与γ结合并将其从αβ上物理性地带走，从而刺激磷酸二酯酶的活性。
