Structure of the turkey erythrocyte adenylate cyclase system.

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Abstract
Target analysis of the turkey erythrocyte adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] system showed that the MW of the ground state enzyme increases from 92,000 with MnATP as substrate and no stimulatory ligands to 226,000 when activated by F- or by 5''-guanyl imidodiphosphate (p[NH]ppG) subsequent to clearance of previously bound GDP. The identical increment in size (130,000) suggests that the same regulatory unit is involved in the activation by both effectors. When assayed with isoproterenol and p[NH]ppG, the enzyme system displayed a further increment in size of 90,000 daltons. Based on binding of the antagonist 125I-labeled hydroxybenzylpindolol, the .beta.-adrenergic receptor is about 90,000 daltons or the same as that seen for activation of the enzyme by isoproterenol through the .beta.-adrenergic-receptor. Because single targets were seen for the ground state enzyme system under all conditions, it would appear that the various regulatory and catalytic components are structurally linked prior to activation by hormone, guanine nucleotides and F-. Based on reported subunit sizes of the nucleotide regulatory and receptor components, it would appear from target analysis that these components are composed of multiple subunits, either homologous or heterologous in structure.