Download Molecular Architecture and a Plausible Mechanical Motion of

Molecular Architecture and Mechanical Motion of Lon, a
Protease-Chaperone Machine
Sun-Shin Cha
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Marine Biotechnology Research Division, Korea Institute of Ocean Science and Technology
Department of Marine Biotechnology, University of Science and Technology
The ATP-dependent Lon protease, which has orthologs distributed in all kingdoms of
life, is essential in bacteria and other microorganisms under stress conditions and is needed
for survival of mammalian cells subjected to oxidative damage. Lon consists of a molecular
chaperone belonging to the AAA+ family and a protease with a serine-lysine catalytic dyad
encoded in tandem in a single polypeptide. Here, we report the 2.0 Å resolution crystal
structure of Lon from Thermococcus onnurineus NA1 (TonLon). Six subunits of TonLon
assemble into a cylindrical structure with a sequestered internal chamber harboring the
proteolytic active sites accessible only through restricted axial channels. Alternating
subunits exist in two different nucleotide states displaying different domain orientations
and intersubunit contacts indicative of the ATP hydrolysis-coupled motions driving protein
unfolding and translocation.