INTERESTING AND UNUSUAL FEATURES IN THE SEQUENCE OF NEUROSPORA-CRASSA MITOCHONDRIAL TYROSINE TRANSFER-RNA

The mitochondrial tyrosine tRNA from Neurospora crassa has been sequenced and found to have several interesting features: (i) It resembles prokaryotic rather than eukaryotic tyrosine tRNAs in that it possesses a large variable loop (loop III); moreover, it can be quantitatively aminoacylated by Escherichia coli tyrosyl-tRNA synthetase but not by yeast tyrosyl-tRNA synthetase. (ii) This tRNA differs from all tRNAs sequenced to date in lacking the A residue at position 14 and the constant purine residue at position 15, two nucleosides that have been found so far in loop I of all tRNAs and that have been implicated in base-base tertiary interactions, respectively, with the universal U residue at position 8 and the constant pyrimidine residue at the end of loop III. (iii) Unlike the N. crassa mitochondrial initiator tRNA, this tRNA contains the usual TIC sequence in loop IV and the highly conserved GG sequence in loop I common to other tRNAs.