Asymmetric allosteric signaling in aspartate transcarbamoylase.

ABSTRACT: Here we use the fluorescence from a genetically encoded unnatural amino acid, l-(7-hydroxycoumarin-4-yl)ethylglycine (HCE-Gly), replacing an amino acid in the regulatory site of Escherichia coli aspartate transcarbamoylase (ATCase) to decipher the molecular details of regulation of this allosteric enzyme. The fluorescence of HCE-Gly is exquisitely sensitive to the binding of all four nucleotide effectors. Although ATP and CTP are primarily responsible for influencing enzyme activity, the results of our fluorescent binding studies indicate that UTP and GTP bind with similar affinities, suggesting a dissociation between nucleotide binding and control of enzyme activity. Furthermore, while CTP is the strongest regulator of enzyme activity, it binds selectively to only a fraction of regulatory

SUBMITTER: Mendes KR 

PROVIDER: S-EPMC3004224 | biostudies-literature | 2010 May

REPOSITORIES: biostudies-literature