Evidence that cysteine-166 is the active-site nucleophile of Pseudomonas aeruginosa amidase: crystallization and preliminary X-ray diffraction analysis of the enzyme.
Biochem J
; 340 ( Pt 3): 711-4, 1999 Jun 15.
Article
em En
| MEDLINE
| ID: mdl-10359655
ABSTRACT
Wild-type and site-specific mutants C166S and C166A (Cys-166-->Ser and Cys-166-->Ala respectively) of the amidase (acylamide amidohydrolase, EC 3.5.1.4) from Pseudomonas aeruginosa were expressed in Escherichia coli by using the vector pKK223-3. Both mutant proteins were catalytically inactive but showed complete cross-reactivity with polyclonal antiserum raised against the wild-type enzyme, as well as CD spectra identical with that of the wild-type enzyme, which were indicative of correct folding. Cys-166 is therefore implicated as the active-site nucleophile. Titration of free thiol groups with 5,5'-dithiobis-(2-nitrobenzoic acid) indicated that Cys-166 is not a rapidly reacting residue. Crystals of both wild-type and C166S amidase grew with identical, rhombohedral morphology; X-ray diffraction analysis established the unit cell dimensions (a=b=c=84 A; alpha=beta=gamma=75 degrees) and space group (R3 or R32). These results imply a quaternary structure of six subunits, with most probably 32 symmetry; the existence of a hexameric structure was supported by molecular mass determinations based on gel filtration and electrophoretic mobility.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Pseudomonas aeruginosa
/
Cisteína
/
Amidoidrolases
Idioma:
En
Revista:
Biochem J
Ano de publicação:
1999
Tipo de documento:
Article
País de afiliação:
Reino Unido