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 · Tue Mar 13 00:00:00 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), Vol. 29:10; ISSN 0006-2960
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
HEME
NUCLEAR MAGNETIC RESONANCE
MYOGLOBIN
CONFORMATIONAL CHANGES
AMINO ACID SEQUENCE
GLUTAMINE
HISTIDINE
MAMMALS
OVERHAUSER EFFECT
PROTONS
AMIDES
AMINO ACIDS
ANIMALS
AZOLES
BARYONS
CARBOXYLIC ACIDS
ELEMENTARY PARTICLES
FERMIONS
GLOBINS
HADRONS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
IMIDAZOLES
MAGNETIC RESONANCE
MOLECULAR STRUCTURE
NUCLEONS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PIGMENTS
PORPHYRINS
PROTEINS
RESONANCE
VERTEBRATES
550601* - Medicine- Unsealed Radionuclides in Diagnostics