Coordination structure of the ferric heme iron in engineered distal histidine myoglobin mutants

Val and His-->Leu, remove the heme-bound water molecule resulting in a five-coordinate heme iron at neutral pH, while the heme-bound water molecule appears to be retained in the engineered myoglobin with His-->Gln substitution as in the wild-type protein. The distal Val and distal Leu ferric myoglobin mutants at neutral pH exhibited EPR spectra with g perpendicular values smaller than 6, which could be interpreted as an admixture of intermediate (S = 3/2) and high (S = 5/2) spin states. At alkaline pH, the distal Gln mutant is in the same so-called "hydroxy low spin" form as the wild-type protein, while the distal Leu and distal Val mutants are in high spin states. The ligand binding properties of these recombinant myoglobin proteins were studied by measurements of azide equilibrium and cyanide binding. The distal Leu and distal Val mutants exhibited diminished azide affinity and extremely slow cyanide binding, while the distal Gln mutant showed azide affinity and cyanide association rate constants similar to those of the wild-type protein. -->
ISSN: 0021-9258
DOI: 10.1016/s0021-9258(18)50024-7
Přístupová URL adresa: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::1a20dee91bc6c73b82b8d39ecd686acd
https://doi.org/10.1016/s0021-9258(18)50024-7
Rights: OPEN
Přírůstkové číslo: edsair.doi.dedup.....1a20dee91bc6c73b82b8d39ecd686acd
Autor: Hiroshi Hori, L.A. Andersson, R C Prince, I J Pickering, C R Sanders nd, Rafael Mattera, G N George, E.J. McKelvey, R.S. Lutz, Masao Ikeda-Saito
Rok vydání: 1992
Předmět:
Zdroj: Scopus-Elsevier
ISSN: 0021-9258
DOI: 10.1016/s0021-9258(18)50024-7
Popis: Recombinant human myoglobin mutants with the distal His residue (E7, His64) replaced by Leu, Val, or Gln residues were prepared by site-directed mutagenesis and expression in Escherichia coli. Electronic and coordination structures of the ferric heme iron in the recombinant myoglobin proteins were examined by optical absorption, EPR, 1H NMR, magnetic circular dichroism, and x-ray spectroscopy. Mutations, His-->Val and His-->Leu, remove the heme-bound water molecule resulting in a five-coordinate heme iron at neutral pH, while the heme-bound water molecule appears to be retained in the engineered myoglobin with His-->Gln substitution as in the wild-type protein. The distal Val and distal Leu ferric myoglobin mutants at neutral pH exhibited EPR spectra with g perpendicular values smaller than 6, which could be interpreted as an admixture of intermediate (S = 3/2) and high (S = 5/2) spin states. At alkaline pH, the distal Gln mutant is in the same so-called "hydroxy low spin" form as the wild-type protein, while the distal Leu and distal Val mutants are in high spin states. The ligand binding properties of these recombinant myoglobin proteins were studied by measurements of azide equilibrium and cyanide binding. The distal Leu and distal Val mutants exhibited diminished azide affinity and extremely slow cyanide binding, while the distal Gln mutant showed azide affinity and cyanide association rate constants similar to those of the wild-type protein.
Databáze: OpenAIRE
Externí odkaz: