title: Resolving individual steps in the operation of ATP-dependent proteolytic molecular machines: from conformational changes to substrate translocation and processivity.
abstract: Clp, Lon, and FtsH proteases are proteolytic molecular machines that use the free energy of ATP hydrolysis to unfold protein substrates and processively present them to protease active sites. Here we review recent biochemical and structural studies relevant to the mechanism of ATP-dependent processive proteolysis. Despite the significant structural differences among the Clp, Lon, and FtsH proteases, these enzymes share important mechanistic features. In these systems, mechanistic studies have provided evidence for ATP binding and hydrolysis-driven conformational changes that drive translocation of substrates, which has significant implications for the processive mechanism of proteolysis. These studies indicate that the nucleotide (ATP, ADP, or nonhydrolyzable ATP analogues) occupancy of the ATPase binding sites can influence the binding mode and/or binding affinity for protein substrates. A general mechanism is proposed in which the communication between ATPase active sites and protein substrate binding regions coordinates a processive cycle of substrate binding, translocation, proteolysis, and product release.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA. lichts@mit.edu
authors.forename: Stuart
authors.initials: S
authors.lastname: Licht
authors.forename: Irene
authors.initials: I
authors.lastname: Lee
mesh_terms: D049069:ATP-Dependent Proteases / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D049071:Endopeptidase Clp / Q000737:chemistry / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000378:metabolism; D007700:Kinetics; D008956:Models, Chemical; D049070:Protease La / Q000737:chemistry / Q000378:metabolism; D011487:Protein Conformation; D020836:Protein Structure, Quaternary
chemical_list: D029968:Escherichia coli Proteins; D049069:ATP-Dependent Proteases; C513383:FtsH protein, E coli; D049070:Protease La; D049071:Endopeptidase Clp