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Elimination of cooperativity in aspartate transcarbamylase by nitration of a single tyrosine residue.

Authors :
Landfear SM
Evans DR
Lipscomb WN
Source :
Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 1978 Jun; Vol. 75 (6), pp. 2654-8.
Publication Year :
1978

Abstract

In a previous report [Landfear, S. M., Lipscomb, W. N. & Evans, D.R. (1978) J. Biol. Chem. 253, 3988--3996] we demonstrated that tetranitromethane can be employed to nitrate a limited number of tyrosine residues in aspartate transcarbamylase (carbamoylphosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2); such modification eliminates cooperativity, feedback inhibition, and enzymatic activity, and reduces binding of the feedback inhibitor cytidine triphosphate. Cooperativity is lost more rapidly than other properties, and this loss correlates with the nitration of a single tyrosine residue. In this paper, we describe the saturation kinetics of hybrid species constructed from nitrated subunits of one type (either catalytic or regulatory) and native subunits of the other type. We conclude that the modification responsible for loss of cooperativity is on the catalytic subunit. The tryptic peptide containing this modification has been isolated and identified.

Details

Language :
English
ISSN :
0027-8424
Volume :
75
Issue :
6
Database :
MEDLINE
Journal :
Proceedings of the National Academy of Sciences of the United States of America
Publication Type :
Academic Journal
Accession number :
26914
Full Text :
https://doi.org/10.1073/pnas.75.6.2654