Papers by Manajit Hayer-Hartl
Nature Structural & Molecular Biology, 1995
Cell Reports, Jul 1, 2019
Highlights d Acute heat stress causes unfolding of a thermo-sensitive subproteome in E. coli d Dn... more Highlights d Acute heat stress causes unfolding of a thermo-sensitive subproteome in E. coli d DnaK (Hsp70) markedly stabilizes most thermo-sensitive proteins d Numerous essential ribosomal proteins are conformationally stabilized by DnaK d Other DnaK-stabilized proteins tend to be large, multidomain, and hetero-oligomeric
Cell, 2007
Kingdom Organism Chaperone/Protein Data Bank ID Monomer (kDa)/ Oligomeric State Cochaperone/Cofac... more Kingdom Organism Chaperone/Protein Data Bank ID Monomer (kDa)/ Oligomeric State Cochaperone/Cofactor Subcellular Localization/Activity Hsp70 System Eubacteria E. coli DnaK/1DKG; 1DKZ 69/monomer DnaJ, GrpE, ClpB Cytosol/folding of nascent proteins; export of some proteins; reactivates heat-inactivated proteins; facilitates abnormal protein degradation; works with ClpB in protein aggregate disassembly; regulates heat-shock response. Archaea Methanosarcinae DnaK 67/monomer DnaJ, GrpE Cytosol/similar to bacterial DnaK. Eukaryotes S. cerevisiae Ssa1-4 70/monomer Ydj1, Sis1, Sti1, Snl1, Fes1, Sse1/2, Cns1 Cytosol/folding of newly synthesized proteins; protein transport into ER, mitochondria. Ssb1,2 66/monomer Zuotin, Sse1/2, Ssz1 Cytosol/folding of ribosome-bound nascent chains. Pdr13p/Ssz1 58/heterodimer Zuotin Cytosol/Zuotin cofactor; modifies Zuotin-Ssb interaction; folding of nascent chains on ribosomes. Sse1/2 77/monomer; heterodimer Ssa1, Ssb1, Sis1 Cytosol/nucleotide exchange factor for Ssa and Ssb Hsp70s; participates in protein folding and refolding.
Nature Structural & Molecular Biology, Nov 1, 1998
FEBS Letters, Jun 12, 2020
Molecular chaperones are highly conserved proteins that promote proper folding of other proteins ... more Molecular chaperones are highly conserved proteins that promote proper folding of other proteins in vivo. Diverse chaperone systems assist de novo protein folding and trafficking, the assembly of oligomeric complexes, and recovery from stress-induced unfolding. A fundamental function of molecular chaperones is to inhibit unproductive protein interactions by recognizing and protecting hydrophobic surfaces that are exposed during folding or following proteotoxic stress. Beyond this basic principle, it is now clear that chaperones can also actively and specifically accelerate folding reactions in an ATP-dependent manner. We focus on the bacterial Hsp70 and chaperonin systems as paradigms, and review recent work that has advanced our understanding of how these chaperones act as catalysts of protein folding.
Science, Mar 8, 2002
Efficient folding of many newly synthesized proteins depends on assistance from molecular chapero... more Efficient folding of many newly synthesized proteins depends on assistance from molecular chaperones, which serve to prevent protein misfolding and aggregation in the crowded environment of the cell. Nascent chain-binding chaperones, including trigger factor, Hsp70, and prefoldin, stabilize elongating chains on ribosomes in a nonaggregated state. Folding in the cytosol is achieved either on controlled chain release from these factors or after transfer of newly synthesized proteins to downstream chaperones, such as the chaperonins. These are large, cylindrical complexes that provide a central compartment for a single protein chain to fold unimpaired by aggregation. Understanding how the thousands of different proteins synthesized in a cell use this chaperone machinery has profound implications for biotechnology and medicine.
Nature Reviews Molecular Cell Biology, Sep 23, 2013
Journal of Biological Chemistry, Sep 1, 2002
The EMBO Journal, Jul 1, 1994
The chaperonin GroEL binds unfolded polypeptides, preventing aggregation, and then mediates their... more The chaperonin GroEL binds unfolded polypeptides, preventing aggregation, and then mediates their folding in an ATP-dependent process. To understand the structural features in non-native polypeptides recognized by GroEL, we have used a-lactalbumin (aLA) as a model substrate. aLA (14.2 kDa) is stabilized by four disulfide bonds and a bound Ca2+ ion, offering the possibility of trapping partially folded disulfide intermediates between the native and the fully unfolded state. The conformers of aLA with high affinity for GroEL are compact, containing up to three disulfide bonds, and have significant secondary structure, but lack stable tertiary structure and expose hydrophobic surfaces. Complex formation requires almost the complete aLA sequence and is strongly dependent on salts that stabilize hydrophobic interactions. Unfolding of aLA to an extended state as well as the burial of hydrophobic surface upon formation of ordered tertiary structure prevent the binding to GroEL. Interestingly, GroEL interacts only with a specific subset of the many partially folded disulfide intermediates of aLA and thus may influence in vitro the kinetics of the folding pathways that lead to disulfide bonds with native combinations. We conclude that the chaperonin interacts with the hydrophobic surfaces exposed by proteins in a flexible compact intermediate or molten globule state.
The EMBO Journal, Nov 1, 1996
As a basic principle, assisted protein folding by GroEL has been proposed to involve the disrupti... more As a basic principle, assisted protein folding by GroEL has been proposed to involve the disruption of misfolded protein structures through ATP hydrolysis and interaction with the cofactor GroES. Here, we describe chaperonin subreactions that prompt a re-examination of this view. We find that GroEL-bound substrate polypeptide can induce GroES cycling on and off GroEL in the presence of ADP. This mechanism promotes efficient folding of the model protein rhodanese, although at a slower rate than in the presence of ATP. Folding occurs when GroES displaces the bound protein into the sequestered volume of the GroEL cavity. Resulting native protein leaves GroEL upon GroES release. A single-ring variant of GroEL is also fully functional in supporting this reaction cycle. We conclude that neither the energy of ATP hydrolysis nor the allosteric coupling of the two GroEL rings is directly required for GroEL/GroES-mediated protein folding. The minimal mechanism of the reaction is the binding and release of GroES to a polypeptidecontaining ring of GroEL, thereby closing and opening the GroEL folding cage. The role of ATP hydrolysis is mainly to induce conformational changes in GroEL that result in GroES cycling at a physiologically relevant rate.
Annual Review of Biochemistry, Jun 2, 2013
The biological functions of proteins are governed by their three-dimensional fold. Protein foldin... more The biological functions of proteins are governed by their three-dimensional fold. Protein folding, maintenance of proteome integrity, and protein homeostasis (proteostasis) critically depend on a complex network of molecular chaperones. Disruption of proteostasis is implicated in aging and the pathogenesis of numerous degenerative diseases. In the cytosol, different classes of molecular chaperones cooperate in evolutionarily conserved folding pathways. Nascent polypeptides interact cotranslationally with a first set of chaperones, including trigger factor and the Hsp70 system, which prevent premature (mis)folding. Folding occurs upon controlled release of newly synthesized proteins from these factors or after transfer to downstream chaperones such as the chaperonins. Chaperonins are large, cylindrical complexes that provide a central compartment for a single protein chain to fold unimpaired by aggregation. This review focuses on recent advances in understanding the mechanisms of chaperone action in promoting and regulating protein folding and on the pathological consequences of protein misfolding and aggregation.
Nature, Jul 1, 2011
P roteins are the most versatile and structurally complex biological macromolecules. They are inv... more P roteins are the most versatile and structurally complex biological macromolecules. They are involved in almost every biological process. Mammalian cells typically express in excess of 10,000 different protein species, which are synthesized on ribosomes as linear chains of up to several thousand amino acids. To function, these chains must generally fold into their 'native state' , an ensemble of a few closely related three-dimensional structures 1,2. How this is accomplished and how cells ensure the conformational integrity of their proteome in the face of acute and chronic challenges constitute one of the most fundamental and medically relevant problems in biology. Central to this problem is that proteins must retain conformational flexibility to function, and thus are only marginally thermodynamically stable in their physiological environment. A substantial fraction of all proteins in eukaryotic cells (20-30% of the total in mammalian cells) even seem to be inherently devoid of any ordered three-dimensional structure and adopt folded conformations only after interaction with binding partners 3. Aberrant behaviour of some of these metastable proteins, such as tau and α-synuclein, can give rise to the formation of fibrillar aggregates that are associated with dementia and Parkinson's disease. Thus, protein quality control and the maintenance of proteome homeostasis (known as proteostasis) are crucial for cellular and organismal health. Proteostasis is achieved by an integrated network of several hundred proteins 4 , including, most prominently, molecular chaperones and their regulators, which assist in de novo folding or refolding, and the ubiquitin−proteasome system (UPS) and autophagy system, which mediate the timely removal of irreversibly misfolded and aggregated proteins. Deficiencies in proteostasis have been shown to facilitate the manifestation or progression of numerous diseases, such as neurodegeneration and dementia, type 2 diabetes, peripheral amyloidosis, lysosomal storage disease, cystic fibrosis, cancer and cardiovascular disease. A major risk factor for many of these ailments is advanced age. Indeed, studies in model organisms indicate that ageing is linked to a gradual decline in cellular proteostasis capacity 5,6. Here we discuss recent insights into the mechanisms of chaperoneassisted protein folding and proteome maintenance. We focus on how proteins use the chaperone machinery to navigate successfully the complex folding-energy landscape in the crowded cellular environment. Understanding these reactions will guide future efforts to define the proteostasis network as a target for pharmacological intervention in diseases of aberrant protein folding.
Nitric Oxide, Aug 1, 2001
As a consequence of bacterial infection and the ensuing inflammation, expression of the inducible... more As a consequence of bacterial infection and the ensuing inflammation, expression of the inducible NO synthase results in prolonged synthesis of NO in high concentrations, which among other functions, contributes to the innate defense against the infectious agent. Here we show that NO inhibits the ability of the bacterial cochaperone DnaJ containing a RING finger-like domain to cooperate with the Hsp70 chaperone DnaK in mediating correct folding of denatured rhodanese. This inhibition is accompanied by S-nitrosation of DnaJ as well as by Zn 2؉ release from the protein. In contrast, NO has no effect on the activity of GroEL, a bacterial chaperone without zinc sulfur clusters. Escherichia coli cells lacking the chaperone trigger factor and thus relying on the DnaJ/DnaK system are more susceptible toward NO-mediated cytostasis than are wildtype bacteria. Our studies identify the cochaperone DnaJ as a molecular target for NO. Thus, an encounter of bacterial cells with NO can impair the protein folding activity of the bacterial chaperone system, thereby increasing bacterial susceptibility toward the defensive attack by the host.
Trends in Biochemical Sciences, Sep 1, 2020
A major challenge faced by human civilization is to ensure that agricultural productivity keeps p... more A major challenge faced by human civilization is to ensure that agricultural productivity keeps pace with population growth and a changing climate. All food supply is generated, directly or indirectly, through the process of photosynthesis, with the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzing the assimilation of atmospheric CO2. Despite its pivotal role, Rubisco is a remarkably inefficient enzyme and must be made by plants in large quantities. However, efforts to enhance Rubisco performance by bioengineering have been hampered by its extensive reliance on molecular chaperones and auxiliary factors for biogenesis, metabolic repair, and packaging into membraneless microcompartments. Here, we review recent advances in understanding these complex machineries and discuss their implications for improving Rubisco carboxylase activity with the goal to increase crop yields.
Science, Aug 11, 1995
AMP-PNP, followed by cross-linking and electron microscopic analysis, were compared with a bioche... more AMP-PNP, followed by cross-linking and electron microscopic analysis, were compared with a biochemical binding analysis by equilibrium dialysis, omitting the cross-linking step (Fig. 2). The comparison showed that glutaraldehyde cross-linking under the conditions used in this study measures the occurrence of GroEL:GroES and GroEL:(GroES)2 particles reliably. 22.
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Papers by Manajit Hayer-Hartl