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

Scott Landfear, D. R. Evans, W. N. Lipscomb

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15 Scopus citations


In a previous report it was demonstrated that tetranitromethane can be employed to nitrate a limited number of tyrosine residues in aspartate transcarbamylase (carbamoylphosphate:L-aspartate carbamoyltransferase, EC; 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. It is concluded that the modification responsible for loss of cooperativity is on the catalytic subunit. The tryptic peptide containing this modification has been isolated and identified.

Original languageEnglish (US)
Pages (from-to)2654-2658
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number6
Publication statusPublished - 1978
Externally publishedYes


ASJC Scopus subject areas

  • General
  • Genetics

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