sup 15 N and sup 1 H NMR studies of Rhodospirillum rubrum cytochrome c sub 2

Miscellaneous · Sun Jan 01 00:00:00 EST 1989

OSTI ID:5545434

Yu, Liping

Rhodospirillum rubrum cytochrome c{sub 2} in both oxidation states has been studied by {sup 15}N and {sup 1}H NMR spectroscopy. Significant {sup 15}N and {sup 1}H NMR resonances of the cytochrome c{sub 2} have been assigned. The exchange rates of the nitrogen-bonded protons are found to vary greatly. The ligand His {pi}NH in the reduced state has an exchange rate {approximately}350 times slower than that in the oxidized state, indicating significant changes in the interior hydrophobicity between the two oxidation states. The ligand His is found not to ionize in the neutral pH range. The ionizations of the nonliganded His 42 with an assigned pKa of {approximately}7.0 in the reduced state and an assigned pKa of 6.2 in the oxidized state cause the resonances of a wide range of groups to shift with pH, perhaps by altering the packing of the {Omega} loops which cover that region of the protein. The oxidized protein has been found to have conformational heterogeneity and experiences gross structural changes with a pKa of 9.2, which is due to the displacement of the ligand methionine at high pH. The N-terminus of the protein has a similar pKa of {approximately}8.5 in both oxidation states. However, the mobility of the N-terminus is different, being restricted in the reduced state and very mobile in the oxidized state. The reduced protein is found to be very stable in the pH range between 4.9 and 10.0, but unfolds abruptly at pH above 11.0. The imidazole of His 42 undergoes fast proton exchange in the denatured form in contrast to the tautomerization at an intermediate rate in the native form. The mechanisms underlying the protein denaturation and renaturation are discussed.

• Research Organization: California Univ., Davis, CA (United States)
• OSTI ID: 5545434
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CYTOCHROMES
MOLECULAR STRUCTURE
RHODOSPIRILLUM
BIOCHEMISTRY
CHEMICAL SHIFT
LIGANDS
NITROGEN 15
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
PROTONS
TRACER TECHNIQUES
BACTERIA
BARYONS
CHEMISTRY
ELEMENTARY PARTICLES
FERMIONS
HADRONS
ISOTOPE APPLICATIONS
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MICROORGANISMS
NITROGEN ISOTOPES
NUCLEI
NUCLEONS
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PIGMENTS
PROTEINS
RESONANCE
SPECTRA
STABLE ISOTOPES
550201* - Biochemistry- Tracer Techniques