Effects of the Tyr-67 acetylation on the heme crevice structure of horse heart cytochrome c derivatives

Conference · Thu May 01 04:00:00 EDT 1986 · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)

OSTI ID:5179890

Miller, L G; Nieman, R A; Cronin, J R

Crystal structures of several cytochromes c indicate that the phenolic group of Tyr-67 (or its homologue) participates in hydrogen bonding interactions within the heme crevice that are significantly affected by oxidation/reduction of the cytochrome. Tyr-67 of N-epsilon-guanidinated cytochrome c (Guan cyt c) and N-epsilon-acetimidylated cytochrome c (Acim cyt c) can be specifically and quantitatively O-acetylated with 3mM N-acetylimidazole. The Tyr-67-acetylated derivatives of Guan cyt c and Acim cyt c (Ac-Guan cyt c and Ac-Acim cyt c) retain the 695 nm absorption band, have a weak negative Cotton effect at 695 nm in their circular dichroism spectra and have almost full activity in the mitochrondrial succinate oxidase system. Cyanide (CN)-, azide-, and imidazole-binding studies were done to evaluate heme ligand stability. Dissociation constants of complexes of the acetylated derivatives are smaller by 10X and 5X than those of cyt c and the unacetylated derivatives, respectively. Pseudofirst order rate constants for CN-binding by Ac-Guan cyt c are 10X and 5X greater than those obtained with cyt c and Guan cyt c. /sup 1/H-NMR was used to evaluate structural changes accompanying Tyr-67 acetylation. The most significant spectral effects of acetylation are +6 ppm and +3 ppm changes in the chemical shifts of the resonances arising from the axial methionine-epsilon-methyl protons and the heme c ring methyl-5 protons, respectively. Acetylation of Tyr-67 appears to alter the position of Met-80 relative to the heme ring.

• Research Organization: Arizona State Univ., Tempe
• OSTI ID: 5179890
• Report Number(s): CONF-8606151-
• Conference Information: Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Journal Volume: 45:6
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
550600 -- Medicine
59 BASIC BIOLOGICAL SCIENCES
62 RADIOLOGY AND NUCLEAR MEDICINE
ACETYLATION
ACYLATION
AMINO ACIDS
AZIDES
AZOLES
BIOCHEMICAL REACTION KINETICS
CARBOXYLIC ACIDS
CHEMICAL REACTIONS
CHEMICAL SHIFT
CYANIDES
CYTOCHROMES
DICHROISM
HEME
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HYDROXY ACIDS
IMIDAZOLES
KINETICS
LIGANDS
MAGNETIC CIRCULAR DICHROISM
MAGNETIC RESONANCE
MOLECULAR STRUCTURE
NITROGEN COMPOUNDS
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PIGMENTS
PORPHYRINS
PROTEINS
REACTION KINETICS
RESONANCE
SPECTRA
TYROSINE