Allosteric transition of aspartokinase I-homoserine dehydrogenase I studied by time-resolved fluorescence.
Biochimie
; 70(12): 1807-14, 1988 Dec.
Article
em En
| MEDLINE
| ID: mdl-3150686
ABSTRACT
The allosteric transition of threonine-sensitive aspartokinase I-homoserine dehydrogenase I from Escherichia coli has been studied by time-resolved fluorescence spectroscopy. Fluorescence decay can be resolved into 2 distinct classes of tryptophan emitters a fast component, with a lifetime of about 1.5 ns; and a slow component, with a lifetime of about 4.5 ns. The fluorescence properties of the slow component are modified by the allosteric transition. In the T-form of the enzyme stabilized by threonine, the lifetime of the slow component is longer, with a red-shifted spectrum; its accessibility to quenching by acrylamide becomes slightly higher without any decrease of fluorescence anisotropy. These results indicate a change in polarity of the slow component environment. The quaternary structure change associated with the allosteric transition probably involves global movements of structural domains without leading to any local mobility on the nanosecond time-scale. We suggest that the slow component corresponds to the unique tryptophan of the buried kinase domain.
Buscar no Google
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Aspartoquinase Homosserina Desidrogenase
/
Complexos Multienzimáticos
Idioma:
En
Revista:
Biochimie
Ano de publicação:
1988
Tipo de documento:
Article
País de afiliação:
França