sup 1 H NMR study of the solution molecular and electronic structure of Escherichia coli ferricytochrome b sub 562 : Evidence for S = 1/2 r reversible S = 5/2 spin equilibrium for intact His/Met ligation

Journal Article · Tue Feb 26 04:00:00 EST 1991 · Biochemistry; (United States)

OSTI ID:5622445

Wu, Jiazhen; La Mar, G N; Yu, L P; Lee, Kang-Bong ^[1]; Walker, F A ^[2]; Chiu, M L; Sligar, S G ^[3]

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1. Univ. of California, Davis (United States)
2. San Francisco State Univ., CA (United States)
3. Univ. of Illinois, Urbana (United States)

The solution 500-MHz {sup 1}H NMR spectral parameters for ferricytochrome b{sub 562}, a soluble 12-kDa electron carrier from Escherichia coli with axial His/Met coordination, are shown to be strongly influenced by protein concentration and ionic strength at low pH and 25C in a manner consistent with significant aggregation at low ionic strength. At high ionic strength a well-resolved {sup 1}H NMR spectrum reveals over 40 hyperfine-shifted resonances which arise from two isomeric species in the ratio 2:1. 2D COSY and NOESY maps at 25C for the hyperfine-shifted resonances allow the assignment of a number of axial His resonances and all heme peripheral substituent peaks. The resulting asymmetric heme contact shift patterns, together with the halving of the number of lines when reconstituting with 2-fold symmetric hemin, demonstrate the molecular basis of the solution heterogeneity to be heme orientational disorder. The strongly upfield-shifted axial Met-7 resonances, characteristic of low-spin ferricytochromes c with His/Met ligation, appear upfield only at very low temperatures. At elevated temperatures, all resonances, in particular those of the axial Met, move strongly downfield. The contact shifts for a coordinated Met in the high-spin state are estimated. A link between equatorial hemin and axial ligand interactions is indicated by a differential population of the high-spin form for the two hemin orientations.

• OSTI ID: 5622445
• Journal Information: Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 30:8; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
AMINO ACIDS
AQUEOUS SOLUTIONS
AZOLES
BACTERIA
BARYONS
CARBOXYLIC ACIDS
CHEMICAL SHIFT
CYTOCHROMES
DISPERSIONS
DRUGS
ELEMENTARY PARTICLES
ESCHERICHIA COLI
FERMIONS
HADRONS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HISTIDINE
HYPERFINE STRUCTURE
IMIDAZOLES
LIPOTROPIC FACTORS
MAGNETIC RESONANCE
METHIONINE
MICROORGANISMS
MIXTURES
NUCLEAR MAGNETIC RESONANCE
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC SULFUR COMPOUNDS
PIGMENTS
PROTEINS
PROTONS
RESONANCE
SOLUTIONS