title: An archaeal peptidase assembles into two different quaternary structures: A tetrahedron and a giant octahedron.
abstract: Cellular proteolysis involves large oligomeric peptidases that play key roles in the regulation of many cellular processes. The cobalt-activated peptidase TET1 from the hyperthermophilic Archaea Pyrococcus horikoshii (PhTET1) was found to assemble as a 12-subunit tetrahedron and as a 24-subunit octahedral particle. Both quaternary structures were solved by combining x-ray crystallography and cryoelectron microscopy data. The internal organization of the PhTET1 particles reveals highly self-compartmentalized systems made of networks of access channels extended by vast catalytic chambers. The two edifices display aminopeptidase activity, and their organizations indicate substrate navigation mechanisms different from those described in other large peptidase complexes. Compared with the tetrahedron, the octahedron forms a more expanded hollow structure, representing a new type of giant peptidase complex. PhTET1 assembles into two different quaternary structures because of quasi-equivalent contacts that previously have only been identified in viral capsids.
authors.affiliation: Laboratoire de Virologie Moléculaire et Structurale c/o EMBL, FRE 2854 CNRS-UJF, 38042 Grenoble, France.
authors.forename: Guy
authors.initials: G
authors.lastname: Schoehn
authors.forename: Frédéric M D
authors.initials: FM
authors.lastname: Vellieux
authors.forename: M
authors.initials: M
authors.lastname: Asunción Durá
authors.forename: Véronique
authors.initials: V
authors.lastname: Receveur-Bréchot
authors.forename: Céline M S
authors.initials: CM
authors.lastname: Fabry
authors.forename: Rob W H
authors.initials: RW
authors.lastname: Ruigrok
authors.forename: Christine
authors.initials: C
authors.lastname: Ebel
authors.forename: Alain
authors.initials: A
authors.lastname: Roussel
authors.forename: Bruno
authors.initials: B
authors.lastname: Franzetti
mesh_terms: D000595:Amino Acid Sequence; D000626:Aminopeptidases / Q000737:chemistry* / Q000378:metabolism; D002213:Capsid / Q000737:chemistry; D002384:Catalysis; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D019281:Dimerization; D006868:Hydrolysis; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D011487:Protein Conformation; D020836:Protein Structure, Quaternary; D019711:Pyrococcus / Q000201:enzymology*; D017386:Sequence Homology, Amino Acid
chemical_list: D010455:Peptides; D000626:Aminopeptidases