title: Oligomeric structure of the ATP-dependent protease La (Lon) of Escherichia coli.
abstract: Lon, also known as protease La, belongs to a class of ATP-dependent serine protease. It plays an essential role in degradation of abnormal proteins and of certain short-lived regulatory proteins, and is thought to possess a Ser-Lys catalytic dyad. To examine the structural organization of Lon, we performed an electron microscope analysis. The averaged images of Lon with end-on orientation revealed a six-membered, ring-shaped structure with a central cavity. The side-on view showed a two-layered structure with an equal distribution of mass across the equatorial plane of the complex. Since a Lon subunit possesses two large regions containing nucleotide binding and proteolytic domains, each layer of the Lon hexamer appears to consist of the side projections of one of the major domains arranged in a ring. Lon showed a strong tendency to form hexamers in the presence of Mg(2+), but dissociated into monomers and/or dimers in its absence. Moreover, Mg(2+)-dependent hexamer formation was independent of ATP. These results indicate that Lon has a hexameric ring-shaped structure with a central cavity, and that the establishment of this configuration requires Mg(2+), but not ATP.
authors.affiliation: Division of Applied Life Science, Gyeongsang National University, Jinju 660-701, Korea.
authors.forename: Seong-Cheol
authors.initials: SC
authors.lastname: Park
authors.forename: Baolei
authors.initials: B
authors.lastname: Jia
authors.forename: Jae-Kyung
authors.initials: JK
authors.lastname: Yang
authors.forename: Duyet Le
authors.initials: DL
authors.lastname: Van
authors.forename: Yong Gi
authors.initials: YG
authors.lastname: Shao
authors.forename: Sang Woo
authors.initials: SW
authors.lastname: Han
authors.forename: Young-Joo
authors.initials: YJ
authors.lastname: Jeon
authors.forename: Chin Ha
authors.initials: CH
authors.lastname: Chung
authors.forename: Gang-Won
authors.initials: GW
authors.lastname: Cheong
mesh_terms: D049069:ATP-Dependent Proteases / Q000737:chemistry* / Q000648:ultrastructure; D000255:Adenosine Triphosphate / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology*; D008274:Magnesium / Q000494:pharmacology; D008954:Models, Biological; D011108:Polymers; D049070:Protease La / Q000737:chemistry* / Q000648:ultrastructure; D020836:Protein Structure, Quaternary
chemical_list: D011108:Polymers; D000255:Adenosine Triphosphate; D049069:ATP-Dependent Proteases; D049070:Protease La; D008274:Magnesium