Kinetic study on the dimer-tetramer interconversion of phosphorylase b by a stopped-flow X-ray scattering method |
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Authors: | Z X Wang H Tsuruta Y Honda Y Tachi-iri K Wakabayashi Y Amemiya H Kihara |
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Institution: | Jichi Medical School, School of Nursing, Tochigi, Japan. |
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Abstract: | The dimer-tetramer interconversion of phosphorylase b induced by the binding of AMP and Mg2+ was monitored using a stopped-flow X-ray scattering method. The rate constants of this second-order reaction have been determined by a nonlinear least-squares method. Burst phases in both radii of gyration and zero-angle intensities were detected at the initial step of the reaction. This suggests that rapid association might take place, followed by a slow association process of which the kinetics were measured in the present study. The radius of gyration of tetrameric phosphorylase b was determined and found to be in excellent agreement with that of phosphorylase a, but different from that of phosphorylase b reported elsewhere (G. Puchwein, O. Kratky, C. F. Golker and E. Helmreich, Biochemistry 9 (1970) 4691). The reason for this inconsistency is discussed. |
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