Sequence analysis and modelling of the two large subunits of Phosphorylase Kinase

Abstract

Phosphorylase kinase (PhK, 1.3 MDa) is a large hexadecameric complex catalyzing the phosphorylation of glycogen phosphorylase (GP). It consists in four subunits (α, β, γ and δ) present each in four copies (Figure 1). The overall 3D structure of the PhK, obtained at 0.99 nm by cryo-electron microscopy, is presented in another poster at this meeting [1]. This cryo-EM map can be further exploited by fitting the structure at atomic resolution of the different subunits. However, only the experimental structures of the catalytic domain of the γ subunit (two thirds of its polypeptidic chain), and of the δ subunit (intrinsic calmodulin) have been solved. Experimental data are not yet available for the α and β subunits (two thirds of the PhK total mass), which probably arose from gene duplication, and play a key role in the regulation of the enzyme.