Abstract of the PDB Structure's related Publication:
Loss of N7-methylguanosine (m7G) modification is involved in the recently discovered rapid tRNA degradation pathway. In yeast, this modification is catalyzed by the heterodimeric complex composed of a catalytic subunit Trm8 and a noncatalytic subunit Trm82. We have solved the crystal structure of Trm8 alone and in complex with Trm82. Trm8 undergoes subtle conformational changes upon Trm82 binding which explains the requirement of Trm82 for activity. Cocrystallization with the S-adenosyl-methionine methyl donor defines the putative catalytic site and a guanine binding pocket. Small-angle X-ray scattering in solution of the Trm8-Trm82 heterodimer in complex with tRNA(Phe) has enabled us to propose a low-resolution structure of the ternary complex which defines the tRNA binding mode of Trm8-Trm82 and the structural elements contributing to specificity.
AdoMet is the methyl group donor. Heterodimer composed of two unrelated subunits: Trm8p (catalytic subunit) and Trm82p (cofactor, stimulates the activity of Trm8p, but is NOT absolutely essential). Works with Trm82p. Trm8p/Trm82p are not structuraly related. Belongs to the methyltransferase superfamily. TrmB family. This methyltransferase catalyzes the formation of N7-methylguanine at position 46 in tRNAs.
This modification is required to maintain the stability of tRNAs, with its absence resulting in tRNA decay (
Alexandrov et al. 2006).