Substrate-binding subunit of tRNA (adenine-N(1)-)-methyltransferase, which catalyzes the formation of N(1)-methyladenine at position 58 (m1A58) in initiator methionyl-tRNA (PubMed:10779558, PubMed:9851972). Also required for repression of GCN4 mRNA translation by the upstream open reading frames (uORFs) under conditions of amino acid sufficiency (PubMed:7542616). Heterotetramer; composed of two copies of TRM6/GCD10 and two copies of TRM61/GCD14. Present with 2580 molecules/cell in log phase SD medium. Belongs to the TRM6/GCD10 family.