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Role of Escherichia coli heat shock proteins IbpA and IbpB in protection of alcohol dehydrogenase AdhE against heat inactivation in the presence of oxygen

100%
Matuszewska E., Kwiatkowska J., Ratajczak E., Kuczyńska-Wiśnik D., Laskowska E.
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issue 1
55-61
EN
Escherichia coli small heat shock proteins IbpA and IbpB are molecular chaperones that bind denatured proteins and facilitate their subsequent refolding by the ATP-dependent chaperones DnaK/DnaJ/GrpE and ClpB. In vivo, the lack of IbpA and IbpB proteins results in increased protein aggregation under severe heat stress or delayed removal of aggregated proteins at recovery temperatures. In this report we followed the appearance and removal of aggregated alcohol dehydrogenase, AdhE, in E. coli submitted to heat stress in the presence of oxygen. During prolonged incubation of cells at 50°C, when AdhE was progressively inactivated, we initially observed aggregation of AdhE and thereafter removal of aggregated AdhE. In contrast to previous studies, the lack of IbpA and IbpB did not influence the formation and removal of AdhE aggregates. However, in ΔibpAB cells AdhE was inactivated and oxidized faster than in wild type strain. Our results demonstrate that IbpA and IbpB protected AdhE against thermal and oxidative inactivation, providing that the enzyme remained soluble. IbpA and IbpB were dispensable for the processing of irreversibly damaged and aggregated AdhE.
2
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Escherichia coli small heat shock proteins IbpA/B enhance activity of enzymes sequestered in inclusion bodies.

100%
Kuczyńska-Wiśnik D., Żurawa-Janicka D., Narkiewicz J., Kwiatkowska J., Lipińska B., Laskowska E.
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vol. 51
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issue 4
925-931
EN
Escherichia coli small heat shock proteins, IbpA/B, function as molecular chaperones and protect misfolded proteins against irreversible aggregation. IbpA/B are induced during overproduction of recombinant proteins and bind to inclusion bodies in E. coli cells. We investigated the effect of ΔibpA/B mutation on formation of inclusion bodies and biological activity of enzymes sequestered in the aggregates in E. coli cells. Using three different recombinant proteins: Cro-β-galactosidase, β-lactamase and rat rHtrA1 we demonstrated that deletion of the ibpA/B operon did not affect the level of produced inclusion bodies. However, in aggregates containing IbpA/B a higher enzymatic activity was detected than in the IbpA/B-deficient inclusion bodies. These results confirm that IbpA/B protect misfolded proteins from inactivation in vivo.
3
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Molecular mechanisms initiating amyloid β-fibril formation in Alzheimer's disease

75%
Kirkitadze M. D., Kowalska A.
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2005
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vol. 52
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issue 2
417-423
EN
The deposition of aggregated amyloid β-protein (Aβ) in the human brain is a major lesion in Alzheimer' disease (AD). The process of Aβ fibril formation is associated with a cascade of neuropathogenic events that induces brain neurodegeneration leading to the cognitive and behavioral decline characteristic of AD. Although a detailed knowledge of Aβ assembly is crucial for the development of new therapeutic approaches, our understanding of the molecular mechanisms underlying the initiation of Aβ fibril formation remains very incomplete. The genetic defects responsible for familial AD influence fibrillogenesis. In a majority of familial cases determined by amyloid precursor protein (APP) and presenilin (PS) mutations, a significant overproduction of Aβ and an increase in the Aβ42/Aβ40 ratio are observed. Recently, it was shown that the two main alloforms of Aβ have distinct biological activity and behaviour at the earliest stage of assembly. In vitro studies demonstrated that Aβ42 monomers, but not Aβ40, form initial and minimal structures (pentamer/hexamer units called paranuclei) that can oligomerize to larger forms. It is now apparent that Aβ oligomers and protofibrils are more neurotoxic than mature Aβ fibrils or amyloid plaques. The neurotoxicity of the prefibrillar aggregates appears to result from their ability to impair fundamental cellular processes by interacting with the cellular membrane, causing oxidative stress and increasing free Ca^(2+)that eventually lead to apoptotic cell death.
4
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3D Domain swapping, protein oligomerization, and amyloid formation.

75%
Jaskólski M.
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2001
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vol. 48
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issue 4
807-827
EN
In 3D domain swapping, first described by Eisenberg, a structural element of a monomeric protein is replaced by the same element from another subunit. This process requires partial unfolding of the closed monomers that is then followed by adhesion and reconstruction of the original fold but from elements contributed by different subunits. If the interactions are reciprocal, a closed-ended dimer will be formed, but the same phenomenon has been suggested as a mechanism for the formation of open-ended polymers as well, such as those believed to exist in amyloid fibrils. There has been a rapid progress in the study of 3D domain swapping. Oligomers higher than dimers have been found, the monomer-dimer equilibrium could be controlled by mutations in the hinge element of the chain, a single protein has been shown to form more than one domain-swapped structure, and recently, the possibility of simultaneous exchange of two structural domains by a single molecule has been demonstrated. This last discovery has an important bearing on the possibility that 3D domain swapping might be indeed an amyloidogenic mechanism. Along the same lines is the discovery that a protein of proven amyloidogenic properties, human cystatin C, is capable of 3D domain swapping that leads to oligomerization. The structure of do-main-swapped human cystatin C dimers explains why a naturally occurring mutant of this protein has a much higher propensity for aggregation, and also suggests how this same mechanism of 3D domain swapping could lead to an open-ended polymer that would be consistent with the cross-β structure, which is believed to be at the heart of the molecular architecture of amyloid fibrils.
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