What is "mt-tw"

Mitochondrially encoded tRNA tryptophan also known as MT-TW is a transfer RNA which in humans is encoded by the mitochondrial MT-TW gene.

MT-TW is a small 68 nucleotide RNA (human mitochondrial map position 5512-5579) that transfers the amino acid tryptophan to a growing polypeptide chain at the ribosome site of protein synthesis during translation.