Mutational analysis of substrate inhibition in tyrosine hydroxylase.
Substrate inhibition in tyrosine hydroxylase (TH) was analyzed by deletion mutagenesis. The deletion mutant TH 156/456 was the smallest section of TH to retain substrate inhibition. The TH 156/456 was monomeric, and so multimer formation does not play a role in substrate inhibition in TH. Further deletion at the N terminus to residue 169 produced a TH molecule with no substrate inhibition but high activity. A mutagenic scan of this region showed that mutations at Trp166 were responsible for this phenotype. A screen of a library of TH molecules containing random mutations identified three other mutants that had lost substrate inhibition but retained high activity. The results in this report are consistent with a model in which substrate inhibition acts through an allosteric mechanism.
Quinsey
N S
NS
Russell Grimwade School of Biochemistry and Molecular Biology, University of Melbourne, Parkville, Victoria, Australia.
Luong
A Q
AQ
Dickson
P W
PW
D000595:Amino Acid Sequence; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004252:DNA Mutational Analysis; D017353:Gene Deletion; D015723:Gene Library; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D013379:Substrate Specificity; D014446:Tyrosine 3-Monooxygenase / Q000737:chemistry / Q000235:genetics*
D014446:Tyrosine 3-Monooxygenase