Crystal structure of a transfer-ribonucleoprotein particle that promotes asparagine formation.
Four out of the 22 aminoacyl-tRNAs (aa-tRNAs) are systematically or alternatively synthesized by an indirect, two-step route requiring an initial mischarging of the tRNA followed by tRNA-dependent conversion of the non-cognate amino acid. During tRNA-dependent asparagine formation, tRNA(Asn) promotes assembly of a ribonucleoprotein particle called transamidosome that allows channelling of the aa-tRNA from non-discriminating aspartyl-tRNA synthetase active site to the GatCAB amidotransferase site. The crystal structure of the Thermus thermophilus transamidosome determined at 3 A resolution reveals a particle formed by two GatCABs, two dimeric ND-AspRSs and four tRNAs(Asn) molecules. In the complex, only two tRNAs are bound in a functional state, whereas the two other ones act as an RNA scaffold enabling release of the asparaginyl-tRNA(Asn) without dissociation of the complex. We propose that the crystal structure represents a transient state of the transamidation reaction. The transamidosome constitutes a transfer-ribonucleoprotein particle in which tRNAs serve the function of both substrate and structural foundation for a large molecular machine.
Blaise
Mickaël
M
Department of Molecular Biology, CARB Centre, University of Aarhus, Arhus C, Denmark. mickael.blaise@gmail.com
Bailly
Marc
M
Frechin
Mathieu
M
Behrens
Manja Annette
MA
Fischer
Frédéric
F
Oliveira
Cristiano L P
CL
Becker
Hubert Dominique
HD
Pedersen
Jan Skov
JS
Thirup
Søren
S
Kern
Daniel
D
D001216:Asparagine / Q000096:biosynthesis*; D003460:Crystallization; D019884:Nitrogenous Group Transferases / Q000378:metabolism; D011487:Protein Conformation; D012348:RNA, Transfer, Asn / Q000378:metabolism*; D012261:Ribonucleoproteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D016963:Thermus thermophilus / Q000378:metabolism; D046249:Transfer RNA Aminoacylation
D012348:RNA, Transfer, Asn; D012261:Ribonucleoproteins; D001216:Asparagine; C412016:Asp-tRNA(Asn) amidotransferase; D019884:Nitrogenous Group Transferases