Proton nuclear magnetic resonance studies on the wild-type and single amino acid substituted tryptophan synthase. cap alpha. -subunits
In order to elucidate the effect of single amino acid substitutions on the conformation of the tryptophan synthase ..cap alpha..-subunit from Escherichia coli in solution, /sup 1/H NMR spectra of the wild-type and mutant proteins were measured at various pHs. Two of the four His C2-proton resonances of the ..cap alpha..-subunit were assigned to two His residues at positions 92 and 146 by using a mutant protein with Thr substituted for the His at position 92. The replacement did not affect the conformation of the protein significantly. The proton resonances of all the Tyr residues in the aromatic region could be picked up from other resonance peaks, employing the wild-type ..cap alpha..-subunit deuteriated at all of the Phe residues. On comparison of the spectra of the wild-type protein with those of the mutant protein with Met substituted for the Glu at position 49, it was concluded that the substitution affects only the residues close to the substituted residue at acidic pH but that a larger part of the protein is affected at alkaline pH. NOE experiments showed that the five Tyr residues, four of which are located in the proximity of position 49, are close to one another. The present results are discussed in the light of the conformational stability of the protein.
- Research Organization:
- Osaka Univ., Japan
- OSTI ID:
- 5932597
- Journal Information:
- Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:18; ISSN BICHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
62 RADIOLOGY AND NUCLEAR MEDICINE
AMINO ACIDS
AROMATICS
AZAARENES
AZOLES
BARYONS
CARBOXYLIC ACIDS
DEUTERIUM COMPOUNDS
ELEMENTARY PARTICLES
ENZYMES
FERMIONS
HADRONS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
INDOLES
MAGNETIC RESONANCE
MOLECULAR STRUCTURE
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PH VALUE
PROTONS
PYRROLES
RESONANCE
SPECTRA
TRANSFERASES
TRYPTOPHAN