Component of the KEOPS complex that is required for the formation of a threonylcarbamoyl group on adenosine at position 37 (t(6)A37) in tRNAs that read codons beginning with adenine. The complex is probably involved in the transfer of the threonylcarbamoyl moiety of threonylcarbamoyl-AMP (TC-AMP) to the N6 group of A37. Bud32 has ATPase activity in the context of the KEOPS complex and likely plays a supporting role to the catalytic subunit Kae1. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Component of the KEOPS complex that consists of Kae1, Bud32, Cgi121 and Pcc1; the whole complex dimerizes. This protein is considered an atypical serine/threonine kinase, because it lacks the conventional structural elements necessary for the substrate recognition as well as a lysine residue that in all other serine/threonine kinases participates in the catalytic event (By similarity). Bud32 has protein kinase activity in vitro, but in the context of the KEOPS complex, the catalytic subunit Kae1 switches the activity of Bud32 from kinase into ATPase (PubMed:23945934). Belongs to the protein kinase superfamily. BUD32 family.