Premium
Localization of the site for the nucleotide effectors of Escherichia coli carbamoyl phosphate synthetase using site‐directed mutagenesis
Author(s) -
Mora Paz,
Rubio Vicente,
Fresquet Vicente,
Cervera Javier
Publication year - 1999
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(99)00197-0
Subject(s) - allosteric regulation , escherichia coli , alanine , biochemistry , activator (genetics) , site directed mutagenesis , carbamoyl phosphate synthetase , nucleotide , mutagenesis , chemistry , binding site , active site , phosphate , mutant , microbiology and biotechnology , biology , amino acid , enzyme , receptor , gene
Replacement by alanine of Ser‐948, Thr‐974 and Lys‐954 of Escherichia coli carbamoyl phosphate synthetase (CPS) shows that these residues are involved in binding the allosteric inhibitor UMP and the activator IMP. The mutant CPSs are active in vivo and in vitro and exhibit normal activation by ornithine, but the modulation by both UMP and IMP is either lost or diminished. The results demonstrate that the sites for UMP and IMP overlap and that the activator ornithine binds elsewhere. Since the mutated residues were found in the crystal structure of CPS near a bound phosphate, Ser‐948, Thr‐974 and Lys‐954 bind the phosphate moiety of UMP and IMP.