/sup 13/C NMR studies of bacterial dihydrofolate reductase containing (methyl-/sup 13/C)methionine and (guanido-/sup 13/C)arginine. [Streptococcus]

Conference · Sun Jan 01 04:00:00 EST 1978

OSTI ID:6744095

Matwiyoff, N A; London, R E; Walker, T E; Blakley, R L; Cocco, L

(Methyl-/sup 13/C)methionine and (guanido-/sup 13/C)arginine have been incorporated with high efficiency by Streptococcus faecium var. Durans strain A into dihydrofolate reductase isoenzyme 2 and /sup 13/C NMR spectra have been obtained for the labeled enzymes and their complexes with substrates, co-factors, and inhibitors. The /sup 13/C NMR spectra exhibit a high degree of discrimination--up to six guanido-/sup 13/C resonances spanning a 1.2 ppM range have been resolved for the eight arginine residues and, under certain conditions, seven methyl-/sup 13/C resonances spanning a 3 ppM chemical shift range have been resolved for the seven methionine residues of the enzyme. The /sup 13/C chemical shifts and spin lattice relaxation times of these distinct, relatively narrow resonances can be interpreted in terms of the conformational states of the enzyme and the interactions of the /sup 13/C-labeled residues with bound ligands. In a larger context, the results reported here provide experimental data which bear on a central question in the use of /sup 13/C NMR spectroscopy to probe the structure of labeled macromolecules, vis.: Where should the /sup 13/C label be incorporated to ensure a relatively narrow resonance whose chemical shift is nonetheless sensitive to perturbations of the macromolecule. Contrary to one accepted view, this study demonstrates that a significant degree of internal motion for a class of amino acid residues is not necessarily incompatible with a large chemical shift dispersion within the class.

• Research Organization: Los Alamos Scientific Lab., NM (USA); Iowa Univ., Iowa City (USA). Coll. of Medicine
• DOE Contract Number: W-7405-ENG-36
• OSTI ID: 6744095
• Report Number(s): LA-UR-78-1492; CONF-780501-4
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
BACTERIA
BIOCHEMICAL REACTION KINETICS
CARBON 13
CARBON ISOTOPES
CARBOXYLIC ACIDS
ENZYMES
EVEN-ODD NUCLEI
ISOTOPES
KINETICS
LIGANDS
LIGHT NUCLEI
LIPOTROPIC FACTORS
MAGNETIC RESONANCE
METHIONINE
MICROORGANISMS
MOLECULAR STRUCTURE
NUCLEAR MAGNETIC RESONANCE
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OXIDOREDUCTASES
REACTION KINETICS
RELAXATION
RESIDUES
RESONANCE
SPECTRA
SPECTROSCOPY
SPIN-LATTICE RELAXATION
STABLE ISOTOPES
STREPTOCOCCUS