The unique anticodon conformation of the organismal initiator tRNA^Met_f is based on the three conserved G-C base pairs in the anticodon stem. Proof of this hypothesis is provided by S1-nuclease digestion of the N.crassa initiator tRNA^Met_f, which has only two G-C base pairs in the anticodon stem. The conformation of this loop is different, and is more like that of an elongator tRNA. N. crassa mitochondrial tRNA^Val has a typical elongator tRNA anticodon loop conformation.