The structure of a member of this family from the hyperthermophilic archaeon Pyrobaculum aerophilum contains a modified histidine residue which is interpreted as stable phosphorylation [1]. In vitro binding studies confirmed that adenosine and AMP but not ADP or ATP bind to the protein [1].

1: The structure of an ancient conserved domain establishes a structural basis for stable histidine phosphorylation and identifies a new family of adenosine-specific kinases. Lott JS, Paget B, Johnston JM, Delbaere LT, Sigrell-Simon JA, Banfield MJ, Baker EN; J Biol Chem. 2006;281:22131-22141. PMID:16737961