Yamazaki A, Yamazaki M, Bondarenko V A, Matsumoto H
Department of Opthalmology, Kresge Eye Institute, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
Biochem Biophys Res Commun. 1996 May 15;222(2):488-93. doi: 10.1006/bbrc.1996.0771.
cGMP phosphodiesterase, a key enzyme in phototransduction, is composed of P alpha beta and two P gamma S. P gamma has two functions in P alpha beta regulation: (I) an inhibitor of cGMP hydrolysis and (II) a stimulator of cGMP binding to their noncatalytic sites. Here we show for the first time that these functions can be discriminated. P gamma release by GTP-bound transducing from P alpha beta was stimulated by NaCl in a concentration-dependent manner. However, phosphodiesterase activity in membranes washed with NaCl-free buffer already reached the maximum level. [3H]-cGMP binding of P alpha beta in membranes washed with NaCl required more P gamma than that in membranes washed without NaCl. Other salts had a similar effect. Identical P gamma was released under different [NaCl]. These results indicate that P gamma for the function (I) is released in low [salt], but P gamma for the function (II) is released in high [salt]. These P gamma functions may be expressed separately in phototransduction.
cGMP磷酸二酯酶是光转导中的关键酶，由Pαβ和两个PγS组成。Pγ在Pαβ调节中具有两种功能：（I）cGMP水解的抑制剂和（II）cGMP与其非催化位点结合的刺激剂。在这里，我们首次表明这些功能可以区分。GTP结合的转导蛋白从Pαβ释放Pγ受到NaCl的浓度依赖性刺激。然而，用无NaCl缓冲液洗涤的膜中的磷酸二酯酶活性已经达到最高水平。用NaCl洗涤的膜中Pαβ的[3H]-cGMP结合比不用NaCl洗涤的膜需要更多的Pγ。其他盐也有类似的效果。在不同的[NaCl]下释放相同的Pγ。这些结果表明，功能（I）的Pγ在低盐浓度下释放，但功能（II）的Pγ在高盐浓度下释放。这些Pγ功能可能在光转导中分别表达。
