Ca2+-induced Structural Changes in Phosphorylase Kinase Detected by Small-angle X-ray Scattering

Overview

Journal Protein Sci

Specialty Biochemistry

Date 2005 Mar 3

PMID 15741333

Citations 15

Authors

Timothy S Priddy

Brian A MacDonald

William T Heller

Owen W Nadeau

Jill Trewhella

Gerald M Carlson

Affiliations

Soon will be listed here.

Abstract

Phosphorylase kinase (PhK), a 1.3-MDa (alphabetagammadelta)(4) hexadecameric complex, is a Ca(2+)-dependent regulatory enzyme in the cascade activation of glycogenolysis. PhK comprises two arched (alphabetagammadelta)(2) octameric lobes that are oriented back-to-back with overall D(2) symmetry and joined by connecting bridges. From chemical cross-linking and electron microscopy, it is known that the binding of Ca(2+) by PhK perturbs the structure of all its subunits and promotes redistribution of density throughout both its lobes and bridges; however, little is known concerning the interrelationship of these effects. To measure structural changes induced by Ca(2+) in the PhK complex in solution, small-angle X-ray scattering was performed on nonactivated and Ca(2+)-activated PhK. Although the overall dimensions of the complex were not affected by Ca(2+), the cation did promote a shift in the distribution of the scattering density within the hydrated volume occupied by the PhK molecule, indicating a Ca(2+)-induced conformational change. Computer-generated models, based on elements of the known structure of PhK from electron microscopy, were constructed to aid in the interpretation of the scattering data. Models containing two ellipsoids and four cylinders to represent, respectively, the lobes and bridges of the PhK complex provided theoretical scattering profiles that accurately fit the experimental data. Structural differences between the models representing the nonactivated and Ca(2+)-activated conformers of PhK are consistent with Ca(2+)-induced conformational changes in both the lobes and the interlobal bridges.

Citing Articles

Activation of Phosphorylase Kinase by Physiological Temperature.

Herrera J, Thompson J, Rimmer M, Nadeau O, Carlson G Biochemistry. 2015; 54(51):7524-30.

PMID: 26632861 PMC: 5014378. DOI: 10.1021/acs.biochem.5b01032.

Mass Spectrometric Analysis of Surface-Exposed Regions in the Hexadecameric Phosphorylase Kinase Complex.

Rimmer M, Artigues A, Nadeau O, Villar M, Vasquez-Montes V, Carlson G Biochemistry. 2015; 54(46):6887-95.

PMID: 26551836 PMC: 5015440. DOI: 10.1021/acs.biochem.5b00682.

Physicochemical changes in phosphorylase kinase induced by its cationic activator Mg(2+).

Liu W, Nadeau O, Sage J, Carlson G Protein Sci. 2013; 22(4):444-54.

PMID: 23359552 PMC: 3610050. DOI: 10.1002/pro.2226.

Structure and location of the regulatory β subunits in the (αβγδ)4 phosphorylase kinase complex.

Nadeau O, Lane L, Xu D, Sage J, Priddy T, Artigues A J Biol Chem. 2012; 287(44):36651-61.

PMID: 22969083 PMC: 3481268. DOI: 10.1074/jbc.M112.412874.

Mass spectrometry reveals differences in stability and subunit interactions between activated and nonactivated conformers of the (αβγδ)4 phosphorylase kinase complex.

Lane L, Nadeau O, Carlson G, Robinson C Mol Cell Proteomics. 2012; 11(12):1768-76.

PMID: 22964223 PMC: 3518106. DOI: 10.1074/mcp.M112.021394.

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