Nuclear magnetic resonance studies on bacterial dihydrofolate reductase containing (guanidino-/sup 13/C)arginine. [Streptococcus]

Journal Article · Tue Oct 03 04:00:00 EDT 1978 · Biochemistry; (United States)

OSTI ID:6531858

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

Dihydrofolate reductase labeled with (guanidino-/sup 13/C)arginine has been purified from Streptococcus faecium and /sup 13/C nuclear magnetic resonance spectra of the enzyme and its complexes with various ligands have been recorded. Resonances of the eight residues are resolved into 4 to 6 peaks with chemical shifts over a range of 1.2 ppM. There appear to be two classes of residues: those with chemical shifts very close to that of free (guanidino-/sup 13/C)arginine (class 1); and those with significantly different shifts (class 2). Spin-lattice relaxation times (T/sub 1/), measured in H/sub 2/O, for residues of class 1 are approximately 50% greater than the values for residues of the second class. In D/sub 2/O the T/sub 1/ values for both classes of residues are essentially the same and approximately twice the values obtained in H/sub 2/O for residues of class 1. The temperature-dependent behavior of T/sub 1/ for residues of class 2, together with the small nuclear Overhauser enhancement values, and the difference in line width in H/sub 2/O vs. D/sub 2/O are consistent with the assumption that the internal motion of these residues is slow relative to the overall rotational motion of the protein. An overall rotational correlation time for the protein of 20 ns has been estimated from the data for these immobilized residues. Class 1 residues appear to have a significant degree of internal motion and are probably accessible to solvent, whereas class 2 residues are probably inaccessible.

• OSTI ID: 6531858
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 17:20; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

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