The chaperonin GroEL binds a polypeptide in an alpha-helical conformation.
Chaperones facilitate folding and assembly of nascent polypeptides in vivo and prevent aggregation in refolding assays in vitro. A given chaperone acts on a number of different proteins. Thus, chaperones must recognize features present in incompletely folded polypeptide chains and not strictly dependent on primary structural information. We have used transferred nuclear Overhauser effects to demonstrate that the Escherichia coli chaperonin GroEL binds to a peptide corresponding to the N-terminal alpha-helix in rhodanese, a mitochondrial protein whose in vitro refolding is facilitated by addition of GroEL, GroES, and ATP. Furthermore, the peptide, which is unstructured when free in aqueous solution, adopts an alpha-helical conformation upon binding to GroEL. Modification of the peptide to reduce its intrinsic propensity to take up alpha-helical structure lowered its affinity for GroEL, but, nonetheless, it could be bound and took up a helical conformation when bound. We propose that GroEL interacts with sequences in an incompletely folded chain that have the potential to adopt an amphipathic alpha-helix and that the chaperonin binding site promotes formation of a helix.
Landry
S J
SJ
Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas 75235-9041.
Gierasch
L M
LM
D000255:Adenosine Triphosphate / Q000378:metabolism; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism*; D001665:Binding Sites; D018834:Chaperonin 60; D018833:Chaperonins; D002942:Circular Dichroism; D004926:Escherichia coli / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism*; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy; D008928:Mitochondria / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D011487:Protein Conformation; D011506:Proteins / Q000378:metabolism*; D013884:Thiosulfate Sulfurtransferase / Q000378:metabolism*
D001426:Bacterial Proteins; D018834:Chaperonin 60; D006360:Heat-Shock Proteins; D046911:Macromolecular Substances; D011506:Proteins; D000255:Adenosine Triphosphate; D013884:Thiosulfate Sulfurtransferase; D018833:Chaperonins