Formation of active heterologous nitrate reductases between nitrate reductases A and Z of Escherichia coli.
Mol Microbiol
; 6(2): 209-19, 1992 Jan.
Article
em En
| MEDLINE
| ID: mdl-1545705
ABSTRACT
Two nitrate reductases, NRA and NRZ, are present in Escherichia coli. These isoenzymes have the same alpha beta gamma, subunits composition and have similar size and genetic organization. Corresponding subunits of the complexes share at least 75% identity. By subcloning the different genes and expressing them from separate transcriptional units, we have demonstrated (i) that the translation of the subunits and their assembly are not coupled processes, since subunits produced concomitantly but independently can meet efficiently and associate to form active enzymes, and (ii) that the alpha subunit of a given complex can be replaced by its counterpart from the other isoenzyme to yield an active membrane-bound heterologous enzyme. One such heterologous enzyme, alpha A beta Z gamma Z, has been purified; it is less stable than the native enzymes, more susceptible to thermal denaturation, and shows increased sensitivity to proteolysis. It is also less stably bound to the membrane and, consequently, its activity with physiological electron donors is drastically reduced. The possibility that heterologous nitrate reductases could be formed in vivo is discussed with reference to the existence of porin heterotrimers of the outer membrane proteins OmpC, OmpF and PhoE.
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Coleções:
01-internacional
Contexto em Saúde:
3_ND
Base de dados:
MEDLINE
Assunto principal:
Escherichia coli
/
Nitrato Redutases
Idioma:
En
Revista:
Mol Microbiol
Ano de publicação:
1992
Tipo de documento:
Article