In vivo activities of GroEL minichaperones.
Fragments encompassing the apical domain of GroEL, called minichaperones, facilitate the refolding of several proteins in vitro without requiring GroES, ATP, or the cage-like structure of multimeric GroEL. We have identified the smallest minichaperone that is active in vitro in chaperoning the refolding of rhodanese and cyclophilin A: GroEL(193-335). This finding raises the question of whether the minichaperones are active under more stringent conditions in vivo. The smallest minichaperones complement two temperature-sensitive Escherichia coli groEL alleles, EL44 and EL673, at 43 degreesC. Although they cannot replace GroEL in cells in which the chromosomal groEL gene has been deleted by P1 transduction, GroEL(193-335) enhances the colony-forming ability of such cells when limiting amounts of GroEL are expressed from a tightly regulated plasmid. Surprisingly, we found that overexpression of GroEL prevents plaque formation by bacteriophage lambda and inhibits replication of the lambda origin-dependent plasmid, Lorist6. The minichaperones also inhibit Lorist6 replication, but less markedly. The complex quaternary structure of GroEL, its central cavity, and the structural allosteric changes that take place on the binding of nucleotides and GroES are not essential for all of its functions in vivo.
Cambridge Centre for Protein Engineering and Cambridge University Chemical Laboratory, Medical Research Centre, Hills Road, Cambridge CB2 2QH, United Kingdom.
J
J
Chatellier
F
F
Hill
P A
PA
Lund
A R
AR
Fersht
D000483:Alleles; D010582:Bacteriophage lambda / Q000235:genetics / Q000502:physiology; D001483:Base Sequence; D018834:Chaperonin 60 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005816:Genetic Complementation Test; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011487:Protein Conformation; D017510:Protein Folding; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018741:Replication Origin; D013696:Temperature; D014779:Virus Replication
D018834:Chaperonin 60; D017931:DNA Primers; D010446:Peptide Fragments; D011994:Recombinant Proteins