FTIR analysis of the interaction of azide with horse heart myoglobin variants.
Biochemistry
; 33(24): 7600-8, 1994 Jun 21.
Article
em En
| MEDLINE
| ID: mdl-8011626
ABSTRACT
The interaction of azide with variants of horse heart myoglobin (Mb) has been characterized by Fourier transform infrared (FTIR), electron paramagnetic resonance (EPR), and UV-VIS absorption spectroscopy and by molecular modeling calculations. Distal histidine variants (His64Thr, His64Ile, His64Lys) and charged surface variants (Val67Arg, Lys45Glu, Lys45Glu/Lys63Glu) were included in this study. All variants, with the exception of Val67Arg, have a lower azide affinity than the wild-type protein. Analysis of the temperature dependence of the FTIR spectra (277-313 K) revealed that the wild-type protein and all variants exhibit a high-spin/low-spin equilibrium. Introduction of positively charged amino acid residues shifts nu max for the low-spin form to higher energy while negatively charged residues shifted this maximum to lower energy. The low azide binding affinity exhibited by the His64Thr and His64Ile variants is accompanied by a shift of the nu max for the low-spin infrared band to lower energy and by a significant increase in the corresponding half-bandwidths. This observation indicates greater mobility of the bound azide ligand in these variants. The His64Lys variant exhibits two infrared bands attributable to low-spin forms that are assigned to two different conformations of the lysyl residue. In one conformation, the lysine is proposed to form a hydrogen bond with the bound azide similar to that proposed to occur between the distal histidine and bound azide, and in the other conformation no interaction occurs.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Azidas
/
Espectroscopia de Infravermelho com Transformada de Fourier
/
Mioglobina
Limite:
Animals
Idioma:
En
Revista:
Biochemistry
Ano de publicação:
1994
Tipo de documento:
Article
País de afiliação:
Canadá