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Biochem Biophys Res Commun. 1990 Sep 28;171(3):1312-8.

Allosteric control of quaternary states in E. coli aspartate transcarbamylase.

Author information

1
Gibbs Chemical Laboratory, Harvard University, Cambridge, Massachusetts 02138.

Abstract

Changes in the molecular dimensions of ATCase in the unligated T-state are an increase of 0.4 A in the separation of catalytic trimers when ATP binds. When the R-state is produced by binding of phosphonoacetamide and malonate, addition of CTP or CTP + UTP decreases the separation of catalytic trimers by 0.5 A. In the unliganded Glu239----Gln mutant, in which the T-state is destabilized so that the enzyme exists in an intermediate quaternary state, ligation of ATP transforms the mutant enzyme to the R-state, whereas CTP converts this enzyme to the T-state. Thus, this mutant is much more sensitive to heterotropic allosteric control than is the native enzyme. In this communication we propose a preliminary model based on new crystallographic results that heterotropic regulation occurs partly through control of the quaternary structure by these effectors, thus regulating catalysis.

PMID:
2222446
DOI:
10.1016/0006-291x(90)90829-c
[Indexed for MEDLINE]

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