Crystal structure of **Sulfolobus acidocaldarius** aspartate carbamoyltransferase in complex with its allosteric activator CTP

De Vos, Dirk; Xu, Ying; Aerts, Tony; Van Petegem, Filip; Van Beeumen, Jozef J.

doi:10.1016/J.BBRC.2008.04.173

Title

Crystal structure of **Sulfolobus acidocaldarius** aspartate carbamoyltransferase in complex with its allosteric activator CTP

Author

De Vos, Dirk

Xu, Ying

Aerts, Tony

Van Petegem, Filip

Van Beeumen, Jozef J.

Abstract

Aspartate carbamoyltransferase (ATCase) is a paradigm for allosteric regulation of enzyme activity. B-class ATCases display very similar homotropic allosteric behaviour, but differ extensively in their heterotropic patterns. The ATCase from the thermoacidophilic archaeon Sulfolobus acidocaldarius, for example, is strongly activated by its metabolic pathway′s end product CTP, in contrast with Escherichia coli ATCase which is inhibited by CTP. To investigate the structural basis of this property, we have solved the crystal structure of the S. acidocaldarius enzyme in complex with CTP. Structure comparison reveals that effector binding does not induce similar large-scale conformational changes as observed for the E. coli ATCase. However, shifts in sedimentation coefficients upon binding of the bi-substrate analogue PALA show the existence of structurally distinct allosteric states. This suggests that the so-called Nucleotide-Perturbation model for explaining heterotropic allosteric behaviour, which is based on global conformational strain, is not a general mechanism of B-class ATCases.

Language

English

Source (journal)

Biochemical and biophysical research communications. - New York, N.Y.

Publication

New York, N.Y. : 2008

ISSN

0006-291X

DOI

10.1016/J.BBRC.2008.04.173

Volume/pages

372 :1 (2008) , p. 40-44