As part of the ribosome quality control complex (RQC), a ribosome-associated complex, mediates the extraction of incompletely synthesized nascent chains from stalled ribosomes as well as their ubiquitin-mediated proteasomal degradation. Thereby, frees ribosomes from the stalled translation complex and prevents the accumulation of nascent polypeptide chains that are potentially toxic for the cell. Mtr1/rqc2 is responsible for selective recognition of stalled 60S subunits by recognizing an exposed, nascent chain-conjugated tRNA moiety. Mtr1/rqc2 is important for the stable association of the E3 ubiquitin-protein ligase rkr1/ltn1 to the complex. Mtr1/rqc2 recruits alanine- and threonine-charged tRNA to the A site and directs the elongation of stalled nascent chains independently of mRNA or 40S subunits, leading to non-templated C-terminal Ala and Thr extensions (CAT tails). CAT tails induce a heat shock response. Component of the ribosome quality control complex (RQC), composed of the E3 ubiquitin ligase rkr1/ltn1, rqc1 and mtr1/rqc2, as well as cdc48 and its ubiquitin-binding cofactors associated with the 60S ribosomal subunit. RQC2 binds to the 40S-binding surface of tRNAs. Belongs to the NEMF family.