Photoaffinity labelling of cyclic GMP-binding proteins in human platelets.
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.
Department of Pathology, McMaster University, Hamilton, Ontario, Canada.
K M
KM
Tang
J L
JL
Sherwood
R J
RJ
Haslam
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors; D000345:Affinity Labels; D001667:Binding, Competitive; D001792:Blood Platelets / Q000378:metabolism*; D002352:Carrier Proteins / Q000097:blood*; D002462:Cell Membrane / Q000378:metabolism; D000242:Cyclic AMP / Q000494:pharmacology; D006152:Cyclic GMP / Q000097:blood / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D006801:Humans; D007163:Immunosorbent Techniques; D047908:Intracellular Signaling Peptides and Proteins; D008970:Molecular Weight; D010761:Phosphorus Radioisotopes; D010777:Photochemistry; D011494:Protein Kinases / Q000097:blood
D000345:Affinity Labels; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D010761:Phosphorus Radioisotopes; C022994:cyclic GMP-binding protein; D000242:Cyclic AMP; D011494:Protein Kinases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D006152:Cyclic GMP