I'm looking at the net, I find that the tRNA is synthesized in two parts. One is the bulk of the tRNA, the other the stem. That suggests strongly that the stem came later.
I also note that there is a discriminator base at 73. Also that 3/70 pair has 13 variations.
This all strongly suggests that this was not originally an acceptor stem but another closed loop and perhaps a 2nd codon/anticodon region.
Now if I can figure a thermally stabilizing reason WHY tRNA would attach to an AA on one end, and codon on the other, then I'm well on the way.
