Send to

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

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

Author information

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


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.

[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Elsevier Science
Loading ...
Support Center