THUMP from archaeal tRNA:m22G10 methyltransferase, a genuine autonomously folding domain.
The tRNA:m2(2)G10 methyltransferase of Pyrococus abyssi (PAB1283, a member of COG1041) catalyzes the N2,N2-dimethylation of guanosine at position 10 in tRNA. Boundaries of its THUMP (THioUridine synthases, RNA Methyltransferases and Pseudo-uridine synthases)--containing N-terminal domain [1-152] and C-terminal catalytic domain [157-329] were assessed by trypsin limited proteolysis. An inter-domain flexible region of at least six residues was revealed. The N-terminal domain was then produced as a standalone protein (THUMPalpha) and further characterized. This autonomously folded unit exhibits very low affinity for tRNA. Using protein fold-recognition (FR) methods, we identified the similarity between THUMPalpha and a putative RNA-recognition module observed in the crystal structure of another THUMP-containing protein (ThiI thiolase of Bacillus anthracis). A comparative model of THUMPalpha structure was generated, which fulfills experimentally defined restraints, i.e. chemical modification of surface exposed residues assessed by mass spectrometry, and identification of an intramolecular disulfide bridge. A model of the whole PAB1283 enzyme docked onto its tRNA(Asp) substrate suggests that the THUMP module specifically takes support on the co-axially stacked helices of T-arm and acceptor stem of tRNA and, together with the catalytic domain, screw-clamp structured tRNA. We propose that this mode of interactions may be common to other THUMP-containing enzymes that specifically modify nucleotides in the 3D-core of tRNA.
Gabant
Guillaume
G
CEA VALRHO, DSV-DIEP-SBTN, Service de Biochimie post-génomique & Toxicologie Nucléaire, F-30207 Bagnols-sur-Cèze, France.
Auxilien
Sylvie
S
Tuszynska
Irina
I
Locard
Marie
M
Gajda
Michal J
MJ
Chaussinand
Guylaine
G
Fernandez
Bernard
B
Dedieu
Alain
A
Grosjean
Henri
H
Golinelli-Pimpaneau
Béatrice
B
Bujnicki
Janusz M
JM
Armengaud
Jean
J