Autophosphorylation of Mucor rouxii cAMP-dependent protein kinase and its role in holoenzyme activation
Two phosphoproteins of 53,000 and 63,000 mol. wt detected in partially purified preparations of Mucor rouxii cAMP-dependent protein kinase submitted to phosphorylation conditions with [γ- 32 P]ATP are demonstrated to the the result of the autophosphorylation of its regulatory subunit, according to t...
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| Autores principales: | , , |
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| Formato: | JOUR |
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| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_08986568_v4_n4_p443_Rossi |
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| Sumario: | Two phosphoproteins of 53,000 and 63,000 mol. wt detected in partially purified preparations of Mucor rouxii cAMP-dependent protein kinase submitted to phosphorylation conditions with [γ- 32 P]ATP are demonstrated to the the result of the autophosphorylation of its regulatory subunit, according to the following criteria: (1) linearity of phosphate incorporation with enzyme sample; (2) independence of phosphate incorporation on temperature; (3) correlation of the phosphoproteins with enzymatic activity in a DEAE-Sepharose chromatography; (4) specific elution of the phosphorylated proteins from cAMP-agarose; (5) phosphorylation of the purified regulatory subunit. Antibodies specific against Mucor regulatory subunit detected an intact subunit of 72,000 mol. wt in crude extracts. Autophosphorylation of the fungal protein kinase A promotes activation of the holoenzyme by cAMP since: (1) under conditions of partial activations, increase of activity is observed when using the phosphoform of the enzyme; (2) release of free catalytic subunit from cAMP-agarose is enhanced when the holoenzyme is previously phosphorylated. © 1992. |
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