Rearrangement of the distal pocket accompanying E7 His yields Gln substitution in elephant carbonmonoxy- and oxymyoglobin: sup 1 H NMR identification of a new aromatic residue in the heme pocket

Journal Article · Mon Mar 12 23:00:00 EST 1990 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00462a021· OSTI ID:6071322

Yu, L P; La Mar, G N ^[1]; Mizukami, H ^[2]

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1. Univ. of California, Davis (USA)
2. Wayne State Univ., Detroit, MI (USA)

Two-dimensional {sup 1}H NMR methods have been used to assign side-chain resonances for the residues in the distal heme pocket of elephant carbonmonoxymyoglobin (MbCO) and oxymyoglobin (MbO{sub 2}). It is shown that, while the other residues in the heme pocket are minimally perturbed, the Phe CD4 residue in elephant MbCO and MbO{sub 2} resonates considerably upfield compared to the corresponding residue in sperm whale MbCO. The new NOE connectivities to Val E11 and heme-induced ring current calculations indicate that Phe CD4 has been inserted into the distal heme pocket by reorienting the aromatic side chain and moving the CD corner closer to the heme. The C{zeta}H proton of the Phe CD4 was found to move toward the iron of the heme by {approximately}4 {angstrom} relative to the position in sperm whale MbCO, requiring minimally a 3-{angstrom} movement of the CD helical backbone. The significantly altered distal conformation in elephant myoglobin, rather than the single distal E7 substitution, forms a plausible basis for its altered functional properties of lower autoxidation rate, higher redox potential, and increased affinity for CO ligand. These results demonstrate that one-to-one interpretation of amino acid residue substitution (E7 His {yields} Gln) is oversimplified and that conformational changes of substituted proteins which are not readily predicted have to be considered for interpretation of their functional properties.

• OSTI ID: 6071322
• Journal Information: Biochemistry; (USA), Journal Name: Biochemistry; (USA) Vol. 29:10; 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
AMIDES
AMINO ACID SEQUENCE
AMINO ACIDS
ANIMALS
AZOLES
BARYONS
CARBOXYLIC ACIDS
CONFORMATIONAL CHANGES
ELEMENTARY PARTICLES
FERMIONS
GLOBINS
GLUTAMINE
HADRONS
HEME
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
HISTIDINE
IMIDAZOLES
MAGNETIC RESONANCE
MAMMALS
MOLECULAR STRUCTURE
MYOGLOBIN
NUCLEAR MAGNETIC RESONANCE
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OVERHAUSER EFFECT
PIGMENTS
PORPHYRINS
PROTEINS
PROTONS
RESONANCE
VERTEBRATES