The photoaffinity labelling of platelet cyclic GMP (cGMP)-binding proteins by [32P]cGMP was studied; at least five labelled proteins (110, 80, 55, 49 and 38 kDa) were detected in platelet cytosol and four (80, 65, 49 and 38 kDa) in platelet membranes. The 110 kDa species was identified as cGMP-inhibited cyclic AMP (cAMP) phosphodiesterase (PDE III) by immunoprecipitation and by the inhibition of photolabelling by specific inhibitors of this enzyme. Similarly, the 80 kDa species was identified as cGMP-dependent protein kinase by immunoprecipitation and by the effects of cGMP analogues on photolabelling. Addition of cAMP greatly enhanced the labelling of this 80 kDa protein, implying the existence of a potentially important interaction between the effects of cGMP and cAMP. The 65 kDa photolabelled protein appears to be a novel platelet cyclic-nucleotide-binding protein. In contrast, the 49 and 55 kDa photolabelled species are probably the RI and RII regulatory subunits of cAMP-dependent protein kinase, and the 38 kDa protein(s) may be proteolytic fragment(s) of RI and/or RII.
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September 1993
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Research Article|
September 01 1993
Photoaffinity labelling of cyclic GMP-binding proteins in human platelets
K M Tang;
K M Tang
1Department of Pathology, McMaster University, Hamilton, Ontario, Canada L8N 3Z5
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J L Sherwood;
J L Sherwood
1Department of Pathology, McMaster University, Hamilton, Ontario, Canada L8N 3Z5
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R J Haslam
R J Haslam
1Department of Pathology, McMaster University, Hamilton, Ontario, Canada L8N 3Z5
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Publisher: Portland Press Ltd
Online ISSN: 1470-8728
Print ISSN: 0264-6021
© 1993 The Biochemical Society, London
1993
Biochem J (1993) 294 (2): 329–333.
Citation
K M Tang, J L Sherwood, R J Haslam; Photoaffinity labelling of cyclic GMP-binding proteins in human platelets. Biochem J 1 September 1993; 294 (2): 329–333. doi: https://doi.org/10.1042/bj2940329
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