A selection for mutants that interfere with folding of Escherichia coli thioredoxin-1 in vivo
Research output: Contribution to journal › Article › peer-review
Standard
A selection for mutants that interfere with folding of Escherichia coli thioredoxin-1 in vivo. / Huber, Damon; Cha, Myoung-Il; Debarbieux, Laurent; Planson, Anne-Gaëlle; Cruz, Nelly; López, Gary; Tasayco, María Luisa; Chaffotte, Alain; Beckwith, Jon.
In: National Academy of Sciences. Proceedings, Vol. 102, No. 52, 27.12.2005, p. 18872-7.Research output: Contribution to journal › Article › peer-review
Harvard
APA
Vancouver
Author
Bibtex
}
RIS
TY - JOUR
T1 - A selection for mutants that interfere with folding of Escherichia coli thioredoxin-1 in vivo
AU - Huber, Damon
AU - Cha, Myoung-Il
AU - Debarbieux, Laurent
AU - Planson, Anne-Gaëlle
AU - Cruz, Nelly
AU - López, Gary
AU - Tasayco, María Luisa
AU - Chaffotte, Alain
AU - Beckwith, Jon
PY - 2005/12/27
Y1 - 2005/12/27
N2 - Escherichia coli thioredoxin is normally a cytoplasmic protein involved in the reduction of disulfide bonds. However, thioredoxin can be translocated to the periplasm when it is attached to a cotranslational signal sequence. When exported to the periplasm, it can partially replace the activity of DsbA in promoting the formation of disulfide bonds. In contrast, when thioredoxin is fused to a posttranslational signal sequence, very little of it appears in the periplasm. We propose that this absence of posttranslational export is due to the rapid folding of thioredoxin in the cytoplasm. We sought mutants of thioredoxin that retarded its folding in the cytoplasm, which we accomplished by fusing thioredoxin to a posttranslational signal sequence and selecting for mutants in which thioredoxin was exported to the periplasm, where it could replace DsbA. The collection of mutants obtained represents a limited number of amino acid changes in the protein. In vitro studies on purified mutant proteins show that all but one are defective in the kinetics and thermodynamics of protein folding. We propose that the slower folding of the thioredoxin mutant proteins in the cytoplasm allows their export by a posttranslational pathway. We discuss some implications of this class of mutants for aspects of the folding pathway of thioredoxin and for its mechanism of export. In particular, the finding that a folding mutant that allows protein translocation alters an amino acid at the C terminus of the protein suggests that the degree to which thioredoxin folds during its translation must be severely restricted.
AB - Escherichia coli thioredoxin is normally a cytoplasmic protein involved in the reduction of disulfide bonds. However, thioredoxin can be translocated to the periplasm when it is attached to a cotranslational signal sequence. When exported to the periplasm, it can partially replace the activity of DsbA in promoting the formation of disulfide bonds. In contrast, when thioredoxin is fused to a posttranslational signal sequence, very little of it appears in the periplasm. We propose that this absence of posttranslational export is due to the rapid folding of thioredoxin in the cytoplasm. We sought mutants of thioredoxin that retarded its folding in the cytoplasm, which we accomplished by fusing thioredoxin to a posttranslational signal sequence and selecting for mutants in which thioredoxin was exported to the periplasm, where it could replace DsbA. The collection of mutants obtained represents a limited number of amino acid changes in the protein. In vitro studies on purified mutant proteins show that all but one are defective in the kinetics and thermodynamics of protein folding. We propose that the slower folding of the thioredoxin mutant proteins in the cytoplasm allows their export by a posttranslational pathway. We discuss some implications of this class of mutants for aspects of the folding pathway of thioredoxin and for its mechanism of export. In particular, the finding that a folding mutant that allows protein translocation alters an amino acid at the C terminus of the protein suggests that the degree to which thioredoxin folds during its translation must be severely restricted.
KW - Disulfides
KW - Thioredoxins
KW - Magnetic Resonance Spectroscopy
KW - Mutagenesis
KW - Mutagenesis, Site-Directed
KW - Bacterial Proteins
KW - Databases, Protein
KW - Cytoplasm
KW - Escherichia coli
KW - Time Factors
KW - Protein Biosynthesis
KW - Protein Disulfide-Isomerases
KW - Models, Molecular
KW - Protein Processing, Post-Translational
KW - Subcellular Fractions
KW - Circular Dichroism
KW - Protein Sorting Signals
KW - Plasmids
KW - Protein Binding
KW - Oxygen
KW - Blotting, Western
KW - Genetic Techniques
KW - Kinetics
KW - Escherichia coli Proteins
KW - Protein Folding
KW - Protein Structure, Tertiary
KW - Calorimetry, Differential Scanning
KW - Mutation
U2 - 10.1073/pnas.0509583102
DO - 10.1073/pnas.0509583102
M3 - Article
C2 - 16357193
VL - 102
SP - 18872
EP - 18877
JO - Proceedings of the National Academy of Sciences
JF - Proceedings of the National Academy of Sciences
SN - 1091-6490
IS - 52
ER -