Characterization of soluble platelet guanylyl cyclase with peptide antibodies

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Abstract
Soluble guanylyl cyclase partially purified from bovine and human platelets was characterized with antibodies raised against synthetic peptides corresponding to different sequences of the α1- and β1-subunits of the bovine lung enzyme. On immunoblots, the platelet guanylyl cyclase was recognized by the four antisera used, with the exception of an antiserum against the C-terminus of the β1-subunit which did not react with the human platelet but with the bovine platelet β1-subunit. Furthermore the human platelet β1-subunit exhibited a slightly lower molecular mass than the bovine protein. The C-terminal antibodies precipitated native platelet and lung guanylyl cyclase activity. In contrast an antibody against a peptide out of the putative catalytic domain, which is highly conserved between all guanylyl cyclases sequenced so far, did not precipitate native guanylyl cyclase, although it recognized both subunits on immunoblots, suggesting that the respective amino acid sequence is located in an inner site of the protein.