Required for the formation of a threonylcarbamoyl group on adenosine at position 37 (t(6)A37) in tRNAs that read codons beginning with adenine. Is a component of the KEOPS complex that is probably involved in the transfer of the threonylcarbamoyl moiety of threonylcarbamoyl-AMP (TC-AMP) to the N6 group of A37. Kae1 likely plays a direct catalytic role in this reaction, but requires other protein(s) of the complex to fulfill this activity. In vitro, binds tRNA, ssRNA, both single- and double-stranded DNA, and exhibits a low ATPase activity. adenosine(37) in tRNA + L-threonylcarbamoyladenylate = AMP + H(+) + N(6)-L-threonylcarbamoyladenosine(37) in tRNA Binds 1 Fe(2+) ion per subunit. Monomer. Component of the KEOPS complex that consists of Kae1, Bud32, Cgi121 and Pcc1; the whole complex dimerizes. The ATP binding pocket identified in the crystal structure would actually engage the substrate TC-AMP. Belongs to the KAE1 / TsaD family. Was originally (PubMed:17766251) thought to have endonuclease activity, but it could not be confirmed with orthologs purified from M.jannaschii (PubMed:18951093) and S. cerevisiae (PubMed:21183954).