The aminoacceptor stem of the yeast tRNA(Lys) contains determinants of mitochondrial import selectivity

Yeast tRNA(CUU)(Lys) is nucleus-encoded and is partially imported into the mitochondria, Another lysine isoacceptor, tRNA(SUU)(Lys), is also nucleus-e ncoded but is not imported. These two tRNAs differ in 21 bases, We have pre viously localised import selectivity determinants in the anticodon arm. By in vitro import of mutant transcripts and by expression of mutant tRNA gene s in vivo we show here that the first base pair (1:72) and the discriminato r base 73 are also relevant to import selectivity. Replacement of bases 1:7 2 in tRNA(SUU)(Lys) by those of tRNA(CUU)(Lys) makes it importable with a t ransport efficiency similar to natural. (C) 1999 Federation of European Bio chemical Societies.