A nuclear Overhauser effect investigation of the molecular and electronic structure of the heme crevice in lactoperoxidase

Journal Article · Tue Aug 22 00:00:00 EDT 1989 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00443a039· OSTI ID:5432829

Thanabal, V; La Mar, G N ^[1]

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1. Univ. of California, Davis (USA)

The proton homonuclear nuclear Overhauser effect, NOE, in conjunction with paramagnetic-induced dipolar relaxation, is utilized to assign resonances and to probe the molecular and electronic structures of the heme cavity in the low-spin cyanide complex of resting-state bovine lactoperoxidase, LPO-CN. Predominantly primary NOEs were detected in spite of the large molecular weight of the enzyme, which demonstrates again the advantage of paramagnetism suppressing spin diffusion in large proteins. Both of the nonlabile ring protons of a coordinated histidine are located at resonance positions consistent with a deprotonated imidazole. Several methylene proton pairs are identified, of which the most strongly hyperfine-shifted pair is assigned to the unusual chemically functionalized 8-(mercaptomethylene) group of the prosthetic group. The large 8-(mercaptomethylene) proton contact shifts relative to that of the only resolved heme methyl signal are rationalized by the additive perturbations on the rhombic asymmetry of the functionalization of the 8-position and the alignment of the axial histidyl imidazole projection along a vector passing through pyrrole A and C of the prosthetic group. Such a stereochemistry is consistent with the resolution of only a single heme methyl group, 3-CH{sub 3}, as observed. A pair of hyperfine-shifted methylene protons, as well as a low-field hyperfine-shifted labile proton signal, exhibit dipolar connectivities similar to those previously reported for the distal arginine and histidine, respectively, of horseradish peroxidase suggesting that these catalytically relevant residues may also exist in LPO.

• OSTI ID: 5432829
• Journal Information: Biochemistry; (USA), Vol. 28:17; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
PEROXIDASES
NUCLEAR MAGNETIC RESONANCE
CHEMICAL SHIFT
ELECTRONIC STRUCTURE
ENZYME ACTIVITY
HEAVY WATER
LACTIC ACID
MOLECULAR STRUCTURE
NMR SPECTRA
OVERHAUSER EFFECT
PROTONS
STEREOCHEMISTRY
BARYONS
CARBOXYLIC ACIDS
ELEMENTARY PARTICLES
ENZYMES
FERMIONS
HADRONS
HYDROGEN COMPOUNDS
HYDROXY ACIDS
MAGNETIC RESONANCE
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
OXIDOREDUCTASES
OXYGEN COMPOUNDS
RESONANCE
SPECTRA
WATER
550601* - Medicine- Unsealed Radionuclides in Diagnostics