Oligomeric structure of the ATP-dependent protease La (Lon) of Escherichia coli.
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.
Park
Seong-Cheol
SC
Division of Applied Life Science, Gyeongsang National University, Jinju 660-701, Korea.
Jia
Baolei
B
Yang
Jae-Kyung
JK
Van
Duyet Le
DL
Shao
Yong Gi
YG
Han
Sang Woo
SW
Jeon
Young-Joo
YJ
Chung
Chin Ha
CH
Cheong
Gang-Won
GW
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
D011108:Polymers; D000255:Adenosine Triphosphate; D049069:ATP-Dependent Proteases; D049070:Protease La; D008274:Magnesium