Crystal structure of the archaeal asparagine synthetase: interrelation with aspartyl-tRNA and asparaginyl-tRNA synthetases.
J Mol Biol
; 412(3): 437-52, 2011 Sep 23.
Article
en En
| MEDLINE
| ID: mdl-21820443
ABSTRACT
Asparagine synthetase A (AsnA) catalyzes asparagine synthesis using aspartate, ATP, and ammonia as substrates. Asparagine is formed in two steps:
the ß-carboxylate group of aspartate is first activated by ATP to form an aminoacyl-AMP before its amidation by a nucleophilic attack with an ammonium ion. Interestingly, this mechanism of amino acid activation resembles that used by aminoacyl-tRNA synthetases, which first activate the α-carboxylate group of the amino acid to form also an aminoacyl-AMP before they transfer the activated amino acid onto the cognate tRNA. In a previous investigation, we have shown that the open reading frame of Pyrococcus abyssi annotated as asparaginyl-tRNA synthetase (AsnRS) 2 is, in fact, an archaeal asparagine synthetase A (AS-AR) that evolved from an ancestral aspartyl-tRNA synthetase (AspRS). We present here the crystal structure of this AS-AR. The fold of this protein is similar to that of bacterial AsnA and resembles the catalytic cores of AspRS and AsnRS. The high-resolution structures of AS-AR associated with its substrates and end-products help to understand the reaction mechanism of asparagine formation and release. A comparison of the catalytic core of AS-AR with those of archaeal AspRS and AsnRS and with that of bacterial AsnA reveals a strong conservation. This study uncovers how the active site of the ancestral AspRS rearranged throughout evolution to transform an enzyme activating the α-carboxylate group into an enzyme that is able to activate the ß-carboxylate group of aspartate, which can react with ammonia instead of tRNA.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Aspartatoamoníaco Ligasa
/
Pyrococcus abyssi
Idioma:
En
Revista:
J Mol Biol
Año:
2011
Tipo del documento:
Article
País de afiliación:
Francia