Document Type

Article

Publication Title

Protein Science

Publication Date

9-1-1992

Volume

1

Issue

9

Disciplines

Biology | Life Sciences

Abstract

The three‐dimensional structure of an R‐state conformer of glycogen phosphorylase containing the coenzyme‐substrate analog pyridoxal‐5′‐diphosphate at the catalytic site (PLPP‐GPb) has been refined by X‐ray crystallography to a resolution of 2.87 Å. The molecule comprises four subunits of phosphorylase related by approximate 222 symmetry. Whereas the quaternary structure of R‐state PLPP‐GPb is similar to that of phosphorylase crystallized in the presence of ammonium sulfate (Barford, D. & Johnson, L.N., 1989, Nature 340, 609–616), the tertiary structures differ in that the two domains of the PLPP‐GPb subunits are rotated apart by 5° relative to the T‐state conformation. Global differences among the four subunits suggest that the major domains of the phosphorylase subunit are connected by a flexible hinge. The two different positions observed for the terminal phosphate of the PLPP are interpreted as distinct phosphate subsites that may be occupied at different points along the reaction pathway. The structural basis for the unique ability of R‐state dimers to form tetramers results from the orientation of subunits with respect to the dyad axis of the dimer. Residues in opposing dimers are in proper registration to form tetramers only in the R‐state.

DOI

https://doi.org/10.1002/pro.5560010904

Rights

© 1992 The Protein Society

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