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Structure ; 10(1): 33-41, 2002 Jan.
Article in English | MEDLINE | ID: mdl-11796108

ABSTRACT

Phosphorylase kinase (PhK) integrates hormonal and neuronal signals and is a key enzyme in the control of glycogen metabolism. PhK is one of the largest of the protein kinases and is composed of four types of subunit, with stoichiometry (alphabetagammadelta)(4) and a total MW of 1.3 x 10(6). PhK catalyzes the phosphorylation of inactive glycogen phosphorylase b (GPb), resulting in the formation of active glycogen phosphorylase a (GPa) and the stimulation of glycogenolysis. We have determined the three-dimensional structure of PhK at 22 A resolution by electron microscopy with the random conical tilt method. We have also determined the structure of PhK decorated with GPb at 28 A resolution. GPb is bound toward the ends of each of the lobes with an apparent stoichiometry of four GPb dimers per (alphabetagammadelta)(4) PhK. The PhK/GPb model provides an explanation for the formation of hybrid GPab intermediates in the PhK-catalyzed phosphorylation of GPb.


Subject(s)
Glycogen Phosphorylase, Muscle Form/metabolism , Phosphorylase Kinase/chemistry , Protein Structure, Quaternary , Animals , Enzyme Activation , Image Processing, Computer-Assisted , Microscopy, Electron/methods , Models, Biological , Phosphorylase Kinase/metabolism , Phosphorylase Kinase/ultrastructure , Protein Binding , Rabbits , Signal Transduction/physiology
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