Enzyme structure with two catalytic sites for double-sieve selection of substrate.
High-fidelity transfers of genetic information in the central dogma can be achieved by a reaction called editing. The crystal structure of an enzyme with editing activity in translation is presented here at 2.5 angstroms resolution. The enzyme, isoleucyl-transfer RNA synthetase, activates not only the cognate substrate L-isoleucine but also the minimally distinct L-valine in the first, aminoacylation step. Then, in a second, "editing" step, the synthetase itself rapidly hydrolyzes only the valylated products. For this two-step substrate selection, a "double-sieve" mechanism has already been proposed. The present crystal structures of the synthetase in complexes with L-isoleucine and L-valine demonstrate that the first sieve is on the aminoacylation domain containing the Rossmann fold, whereas the second, editing sieve exists on a globular beta-barrel domain that protrudes from the aminoacylation domain.
Nureki
O
O
Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113, Japan.
Vassylyev
D G
DG
Tateno
M
M
Shimada
A
A
Nakama
T
T
Fukai
S
S
Konno
M
M
Hendrickson
T L
TL
Schimmel
P
P
Yokoyama
S
S
D000249:Adenosine Monophosphate; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000201:enzymology; D006860:Hydrogen Bonding; D006868:Hydrolysis; D007532:Isoleucine / Q000378:metabolism*; D007533:Isoleucine-tRNA Ligase / Q000737:chemistry* / Q000378:metabolism; D008956:Models, Chemical; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016296:Mutagenesis; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D012355:RNA, Transfer, Ile / Q000378:metabolism; D013379:Substrate Specificity; D016963:Thermus thermophilus / Q000201:enzymology; D046249:Transfer RNA Aminoacylation; D014633:Valine / Q000378:metabolism*
D012355:RNA, Transfer, Ile; D007532:Isoleucine; D000249:Adenosine Monophosphate; D007533:Isoleucine-tRNA Ligase; D014633:Valine