Internal motions in yeast phenylalanine transfer RNA from /sup 13/C NMR relaxation rates of modified base methyl groups: a model-free approach

Journal Article · Tue Dec 29 04:00:00 EST 1987 · Biochemistry; (United States)

OSTI ID:5408431

Schmidt, P G; Sierzputowska-Gracz, H; Agris, P F

Internal motions at specific locations through yeast phenylalanine tRNA were measured by using nucleic acid biosynthetically enriched in /sup 13/C at modified base methyl groups. Carbon NMR spectra of isotopically enriched tRNA/sup Phe/ reveal 12 individual peaks for 13 of the 14 methyl groups known to be present. The two methyls of N/sup 2/, N/sup 2/-dimethylguanosine (m/sub 2//sup 2/G-26) have indistinguishable resonances, whereas the fourteenth methyl bound to ring carbon-11 of the hypermodified nucleoside 3' adjacent to the anticodon, wyosine (Y-37), does not come from the (methyl-/sup 13/C) methionine substrate. Assignments to individual nucleosides within the tRNA were made on the basis of chemical shifts of the mononucleosides and correlation of /sup 13/C resonances with proton NMR chemical shifts via two-dimensional heteronuclear proton-carbon correlation spectroscopy. Values of /sup 13/C longitudinal relaxation (T/sub 1/) and the nuclear Overhauser enhancements (NOE) were determined at 22.5, 75.5, and 118 MHz for tRNA/sup Phe/ in a physiological buffer solution with 10 mM MgCl/sub 2/, at 22/sup 0/C. These data were used to extract two physical parameters that define the system with regard to fast internal motion: the generalized order parameters (S/sup 2/) and effective correlation times (tau/sub e/) for internal motion of the C-H internuclear vectors. For all methyl groups the generalized order parameter varied from 0.057 to 0.108, compared with the value of 0.111 predicted for a rapidly spinning methyl group rigidly mounted on a spherical macromolecule. Values of tau/sub e/ ranged from 4 to 16 ps, generally shorter times than measured in other work for amino acid methyl groups in several proteins. Somewhat surprising was the finding that the two methyl esters terminating the Y-37 side chain have order parameters similar to those of other methyls in tRNA and only 25% less than that for a methyl directly bonded to the base.

• Research Organization: Huntington Medical Research Institutes, Pasadena, CA (USA)
• OSTI ID: 5408431
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 26:26; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
AMINO ACIDS
CARBON 13
CARBON ISOTOPES
CARBOXYLIC ACIDS
CHEMICAL SHIFT
DRUGS
EVEN-ODD NUCLEI
FUNGI
ISOTOPES
LIGHT NUCLEI
LIPOTROPIC FACTORS
MAGNETIC RESONANCE
METHIONINE
MICROORGANISMS
NUCLEAR MAGNETIC RESONANCE
NUCLEI
NUCLEIC ACIDS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
OVERHAUSER EFFECT
PHENYLALANINE
PLANTS
RESONANCE
RNA
SACCHAROMYCES
SACCHAROMYCES CEREVISIAE
STABLE ISOTOPES
STRUCTURAL MODELS
TRANSFER RNA
YEASTS