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. The Kae1 domain likely plays a direct catalytic role in this reaction (By similarity). The Bud32 domain probably displays kinase activity that regulates Kae1 function. In vitro, exhibits low ATPase activity, but does not bind DNA and does not have endonuclease activity. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] adenosine(37) in tRNA + L-threonylcarbamoyladenylate = AMP + H(+) + N(6)-L-threonylcarbamoyladenosine(37) in tRNA Binds 1 Fe(2+) ion per subunit. Activity provided by the Kae1 region seems to be regulated via phosphorylation by the protein kinase Bud32, which is itself activated by Cgi121. Component of the KEOPS complex that consists of Kae1, Bud32, Cgi121 and Pcc1; the whole complex dimerizes. In the N-terminal section; belongs to the KAE1 / TsaD family. In the C-terminal section; belongs to the protein kinase superfamily. Tyr protein kinase family. BUD32 subfamily.