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KMID : 0578319930030040379
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Molecules and Cells
1993 Volume.3 No. 4 p.379 ~ p.383
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Effect of Calmodulin on the Phosphorylation of the Lens Membrane Sunstrates for Protein Kinase A
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Hur Kyu-Chung
Kim Kyu-Won
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Abstract
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Protein kinase A mediated phosphorylation of the lens membrane substrates was performed using lens homogenates in the presense of adenylate cyclase activators. All three lens membrane substrates (Mr. 18, 26, 28 kDa) were phosphorylated by endogenous protein kinase A. Moreover, the phosphorylation was increased markedly by Ca-´ and forskolin. These results indicate that the endogenous protein kinase activity depends on the cAMP contents produced by the lens adenylate cyclase. However, in the presense of sufficient amount of cAMP, Call inhibits 32P-incorporation into the major substrates in lens homogenate phosphorylation system. When calmodulin inhibitor, calmidazolium, was added to lens homogenate phosphorylation system in the presense of sufficient amount of cAMP, the inhibitory effect of Cat+ on the phosphorylation of the major substrates was abolished. Furthermore, 32P-incorporation into the major lens membeane substrates for protein kinase A was gradually decreased by addition of calmodulin when the urea-washed membranes were phosphorylated with exogenous protein kinase A. These results demonstrate that calmodulin inhibits protein kinase mediated phosphorylation of the lens membrane substrates when sufficient amount of cAMP exist.
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KEYWORD
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