DnaK and DnaJ heat shock proteins participate in protein export in Escherichia coli.
Open accessAbstract
In Escherichia coli secreted proteins must be maintained in an export-competent state before translocation across the cytoplasmic membrane. This function is carried out by a group of proteins called chaperones. SecB is the major chaperone that interacts with precursor proteins before their secretion. We report results indicating that the DnaK and DnaJ heat shock proteins are also involved in the export of several proteins, most likely by acting as their chaperones. Translocation of alkaline phosphatase, a SecB-independent protein, was inhibited in dnaK- and dnaJ- mutant strains, suggesting that export of this protein probably involves DnaK and DnaJ. In addition, DnaK and DnaJ play a critical role in strains lacking SecB. They are required both for viability and for the residual processing of the SecB-dependent proteins LamB and maltose-binding protein (MBP) seen in secB null strains. Furthermore, overproduction of DnaK and DnaJ permits strains lacking SecB to grow in rich medium and accelerates the processing of LamB and MBP. These results suggest that under conditions where SecB becomes limiting, DnaK and DnaJ probably substitute for SecB and facilitate protein export. This provides the cell with a mechanism to overcome a temporary imbalance in the secretion process caused by an abrupt expansion in the pool of precursor proteins.
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When expression is too high, translocation is slowed down by poorly exported proteins or defective signal peptides, so metastable precursors may accumulate in the cytoplasm, promoting inclusion body formation and affecting protein yields and cell viability.
“Indeed, when the expression is too high, the translocation is slowed down by poorly exported proteins or by defective signal peptides, thereby metastable precursors may accumulate in the cytoplasm promoting inclusion bodies formation that affects protein yields and cell viability [141,142].”
From Evolution of Escherichia coli Expression System in Producing Antibody Recombinant Fragments (2020) · cites this paper as [141]
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Experimental — accuracy not yet measuredExcess precursors of secretory proteins in the cytoplasm induce up-regulation of heat shock proteins mediated by sigma factor 32, promoting inclusion body formation and reducing protein yields and cell viability.
“This excess of precursors of secretory proteins in the cytoplasm induces the up-regulation of heat shock proteins, which is mediated by the sigma factor 32 (σ32) [141], promoting inclusion bodies formation, reducing protein yields and cell viability (increased cell toxicity).”
From Evolution of Escherichia coli Expression System in Producing Antibody Recombinant Fragments (2020) · cites this paper as [141]
In “The role of DnaK and DnaJ in a strain lacking SecB” (page unavailable), the paper reports elevated heat-shock protein synthesis when precursor proteins accumulate and proposes a σ32-mediated mechanism. It describes that mechanism as “most likely,” whereas the cited clause states it as established. The citation appears before the separate clause about inclusion bodies, yields, and viability, so those downstream claims are not assessed as attributed to this source. (LLM, conf=0.84)
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References 56 · Cited by 213
Research works printed but not linked: 2
- Inouye, H. and J. Beckwith. 1977. Synthesis and processing of alkaline phosphatase precursor in vitro. Proc. Natl. Acad. Sci. 74: 1440--1444.
- Wild, J., A. Kamath-Loeb, E. Ziegelhoffer, M. Lonetto, Y. Ka- wasaki, and C.A. Gross• 1992. Partial loss of function muta- tions in dnaK, the Escherichia coli hsp70 homologue, affect highly conserved amino acids implicated in ATP binding and hydrolysis. Proc. Natl. Acad. Sci. (in press).
- Authors
- Wild, J., Altman, E., Yura, T., & Gross, C. A.
- Affiliations
- University of Wisconsin–Madison (US)
- ORCID
- Gross, C A
- Venue
- Genes & Development
- Publisher
- Cold Spring Harbor Laboratory
- Published
- 1992-07
- Volume
- 6
- Issue
- 7
- Pages
- 1165-1172
- ISSN
- 0890-9369 (ISSN-L)
- 1549-5477
- OpenAlex
- W2018917459
- Cited by
- 213
- References
- 56
- Citations by year
- 2026: 2 · 2025: 4 · 2024: 2 · 2023: 3 · 2022: 4 · 2021: 6 · 2020: 1 · 2019: 4 · 2018: 3 · 2017: 2 · 2015: 3 · 2014: 6 · 2013: 8 · 2012: 4
- Type
- posted content
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Genes & Development (publishedVersion)
- PubMed (publishedVersion)
- Funders
- National Institutes of Health
- National Institute of General Medical Sciences (GM 36278)
- Topics
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Heat shock proteins research
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Genetics › Bacterial Genetics and Biotechnology
- Life Sciences › Biochemistry, Genetics and Molecular Biology › Endocrinology › Escherichia coli research studies
- Keywords
- DnaK, Hsp40, heat shock proteins, SecB, molecular chaperones, protein secretion, protein export, alkaline phosphatase, lambs, maltose-binding protein, Escherichia coli
- MeSH terms
- Alkaline Phosphatase, Bacterial Proteins, Biological Transport, Active, Escherichia coli, Heat-Shock Proteins, Kinetics, Mutation, HSP70 Heat-Shock Proteins, Escherichia coli Proteins, HSP40 Heat-Shock Proteins
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