Structural analysis of substrate binding by the molecular chaperone DnaK.
DnaK and other members of the 70-kilodalton heat-shock protein (hsp70) family promote protein folding, interaction, and translocation, both constitutively and in response to stress, by binding to unfolded polypeptide segments. These proteins have two functional units: a substrate-binding portion binds the polypeptide, and an adenosine triphosphatase portion facilitates substrate exchange. The crystal structure of a peptide complex with the substrate-binding unit of DnaK has now been determined at 2.0 angstroms resolution. The structure consists of a beta-sandwich subdomain followed by alpha-helical segments. The peptide is bound to DnaK in an extended conformation through a channel defined by loops from the beta sandwich. An alpha-helical domain stabilizes the complex, but does not contact the peptide directly. This domain is rotated in the molecules of a second crystal lattice, which suggests a model of conformation-dependent substrate binding that features a latch mechanism for maintaining long lifetime complexes.
Zhu
X
X
Department of Biochemistry and Molecular Biophysics, College of Physicians and Surgeons, Columbia University, New York 10032, USA.
Zhao
X
X
Burkholder
W F
WF
Gragerov
A
A
Ogata
C M
CM
Gottesman
M E
ME
Hendrickson
W A
WA
D000595:Amino Acid Sequence; D001665:Binding Sites; D018833:Chaperonins / Q000737:chemistry / Q000378:metabolism*; D018360:Crystallography, X-Ray; D004926:Escherichia coli; D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid
D029968:Escherichia coli Proteins; D018840:HSP70 Heat-Shock Proteins; D010455:Peptides; D018833:Chaperonins; C063842:dnaK protein, E coli