Tetrahedral aminopeptidase: a novel large protease complex from archaea

A dodecameric protease complex with a tetrahedral shape (TET) was isolated from Haloarcula marismortui, a salt-loving archaeon. The 42 kDa monomers in the complex are homologous to metal-binding, bacterial aminopeptidases. TET has a broad aminopeptidase activity and can process peptides of up to 30-35 amino acids in length. TET has a central cavity that is accessible through four narrow channels (<17 Angstrom wide) and through four wider channels (21 Angstrom wide). This architecture is different from that of all the proteolytic complexes described to date that are made up by rings or barrels with a single central channel and only two openings.