Crystal Structure of the Archaeal Asparagine Synthetase: Interrelation with Aspartyl-tRNA and Asparaginyl-tRNA Synthetases.Blaise, M., Frechin, M., Olieric, V., Charron, C., Sauter, C., Lorber, B., Roy, H., Kern, D.
(2011) J.Mol.Biol. 412: 437-452
- PubMed: 21820443
- DOI: 10.1016/j.jmb.2011.07.050
- Primary Citation of Related Structures:
- PubMed Abstract:
Asparagine synthetase A (AsnA) catalyzes asparagine synthesis using aspartate, ATP, and ammonia as substrates. Asparagine is formed in two steps: the β-carboxylate group of aspartate is first activated by ATP to form an aminoacyl-AMP before its amida ...
Asparagine synthetase A (AsnA) catalyzes asparagine synthesis using aspartate, ATP, and ammonia as substrates. Asparagine is formed in two steps: the β-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 β-carboxylate group of aspartate, which can react with ammonia instead of tRNA.
Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, Institut de Biologie Moléculaire et Cellulaire, UPR 9002, 15 rue René Descartes, 67084 Strasbourg Cedex, France. email@example.com