1y42

Publication Abstract from PubMed

We determined a 1.95 A X-ray crystal structure of a C-terminally truncated Neurospora crassa mitochondrial tyrosyl-tRNA synthetase (CYT-18 protein) that functions in splicing group I introns. CYT-18's nucleotide binding fold and intermediate alpha-helical domains superimpose on those of bacterial TyrRSs, except for an N-terminal extension and two small insertions not found in nonsplicing bacterial enzymes. These additions surround the cyt-18-1 mutation site and are sites of suppressor mutations that restore splicing, but not synthetase activity. Highly constrained models based on directed hydroxyl radical cleavage assays show that the group I intron binds at a site formed in part by the three additions on the nucleotide binding fold surface opposite that which binds tRNATyr. Our results show how essential proteins can progressively evolve new functions.

A tyrosyl-tRNA synthetase adapted to function in group I intron splicing by acquiring a new RNA binding surface.,Paukstelis PJ, Coon R, Madabusi L, Nowakowski J, Monzingo A, Robertus J, Lambowitz AM Mol Cell. 2005 Feb 4;17(3):417-28. PMID:15694342^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.