Catalytic 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). GCD14 is also required for repression of GCN4 mRNA translation by the upstream open reading frames (uORFs) under conditions of amino acid sufficiency (PubMed:9539420). adenosine(58) in tRNA + S-adenosyl-L-methionine = H(+) + N(1)-methyladenosine(58) in tRNA + S-adenosyl-L-homocysteine Heterotetramer; composed of two copies of TRM6/GCD10 and two copies of TRM61/GCD14. Present with 7220 molecules/cell in log phase SD medium. Belongs to the class I-like SAM-binding methyltransferase superfamily. TRM61 family.