Redox Behavior of the S-Adenosylmethionine (SAM)-Binding Fe-S Cluster in Methylthiotransferase RimO, toward Understanding Dual SAM Activity.
Biochemistry
; 55(41): 5798-5808, 2016 10 18.
Article
em En
| MEDLINE
| ID: mdl-27677419
ABSTRACT
RimO, a radical-S-adenosylmethionine (SAM) enzyme, catalyzes the specific C3 methylthiolation of the D89 residue in the ribosomal S12 protein. Two intact iron-sulfur clusters and two SAM cofactors both are required for catalysis. By using electron paramagnetic resonance, Mössbauer spectroscopies, and site-directed mutagenesis, we show how two SAM molecules sequentially bind to the unique iron site of the radical-SAM cluster for two distinct chemical reactions in RimO. Our data establish that the two SAM molecules bind the radical-SAM cluster to the unique iron site, and spectroscopic evidence obtained under strongly reducing conditions supports a mechanism in which the first molecule of SAM causes the reoxidation of the reduced radical-SAM cluster, impeding reductive cleavage of SAM to occur and allowing SAM to methylate a HS- ligand bound to the additional cluster. Furthermore, by using density functional theory-based methods, we provide a description of the reaction mechanism that predicts the attack of the carbon radical substrate on the methylthio group attached to the additional [4Fe-4S] cluster.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
S-Adenosilmetionina
/
Sulfurtransferases
/
Proteínas Ferro-Enxofre
Idioma:
En
Revista:
Biochemistry
Ano de publicação:
2016
Tipo de documento:
Article
País de afiliação:
França