Rates and energetics of tyrosine ring flips in yeast iso-2-cytochrome c

Journal Article · Tue Aug 21 00:00:00 EDT 1990 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00485a006· OSTI ID:6101789

Nall, B T; Zuniga, E H ^[1]

---

1. Univ. of Texas Health Science Center, San Antonio (USA)

Isotope-edited nuclear magnetic resonance spectroscopy is used to monitor ring flip motion of the five tyrosine side chains in the oxidized and reduced forms of yeast iso-2-cytochrome c. With specifically labeled protein purified from yeast grown on media containing (3,5-{sup 13}C)tyrosine, isotope-edited one-dimensional proton spectra have been collected over a 5-55{degree}C temperature range. The spectra allow selective observation of the 10 3,5 tyrosine ring proton resonances and, using a two-site exchange model, allow estimation of the temperature dependence of ring flip rates from motion-induced changes in proton line shapes. For the reduced protein, tyrosines II and IV are in fast exchange throughout the temperature range investigated, or lack resolvable differences in static chemical shifts for the 3,5 ring protons. Tyrosines I, III, and V are in sloe exchange at low temperatures and in fast exchange at high temperatures. Spectral simulations give flip rates for individual tyrosines in a range of one flip per second at low temperatures to thousands of flips per second at high temperatures. Eyring plots show that two of the tyrosines (I and III) have essentially the same activation parameters. Tentative sequence-specific assignments for the tyrosines in reduced iso-2 are suggested by comparison to horse cytochrome c. For oxidized iso-2, five resonances are observed at high temperatures, suggesting flip rates for all five tyrosines sufficient to average static chemical shift differences. At lower temperatures, there is evidence of intermediate and slow flipping for some of the rings.

• OSTI ID: 6101789
• Journal Information: Biochemistry; (USA), Vol. 29:33; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
CYTOCHROMES
NUCLEAR MAGNETIC RESONANCE
TYROSINE
SPIN FLIP
CARBON 13
CHEMICAL SHIFT
TEMPERATURE DEPENDENCE
YEASTS
AMINO ACIDS
CARBON ISOTOPES
CARBOXYLIC ACIDS
EUMYCOTA
EVEN-ODD NUCLEI
FUNGI
HYDROXY ACIDS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MICROORGANISMS
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
PIGMENTS
PLANTS
PROTEINS
RESONANCE
STABLE ISOTOPES
550601* - Medicine- Unsealed Radionuclides in Diagnostics