Chaperone-like Activity of Bovine Lens α-Crystallin in the Presence of Dithiothreitol-Destabilized Proteins: Characterization of the Formed Complexes

Abgar, Saïd; Yevlampieva, N. P.; Aerts, Tony; Vanhoudt, Jos; Clauwaert, J.

doi:10.1006/bbrc.2000.3518

Cited by 20 publications

(18 citation statements)

References 17 publications

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“…Within these parabolic curves, however, there are certain temporal fluctuations, but nothing that could be perceived as being periodic. These fluctuations may be the signature of the dynamic reorganization of interparticle exchange of ␣-A and ␣-B subunits of ␣-crystallin and denatured ␣-lactalbumin that has been reported in the literature (16,17). The general trend that we characterized as fluffy-ball type of chaperoning complex (1) that may decline in size has also been reported in other DTT denatured proteins (insulin, lysozyme and conalbumin) undergoing chaperoning (17).…”

Section: Discussionsupporting

confidence: 77%

On the Equilibrium between Monomeric α-Lactalbumin and the Chaperoning Complex of α-Crystallin

Neal

Zigler

Bettelheim

2001

Biochemical and Biophysical Research Communications

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Section: Discussionsupporting

confidence: 77%

On the Equilibrium between Monomeric α-Lactalbumin and the Chaperoning Complex of α-Crystallin

Neal

Zigler

Bettelheim

2001

Biochemical and Biophysical Research Communications

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“…Therefore, the whole of these experiments emphasizes the importance of the structural modifications of both ␣-and ␤ LOW /␥-crystallin for the association to take place. On the contrary, the chaperone activity of human recombinant ␣A-or ␣B-crystallin toward other partially unfolded substrates, like insulin or lactalbumin, or thermally denatured alcohol dehydrogenase or citrate synthase, or even ␥D-crystallin, yet denatured by singlet oxygen at 23°C, does not require the ␣-crystallin structural transition (9,14,16,17,20,25,29,56,57).…”

Section: Discussionmentioning

confidence: 99%

Subunit Exchange Demonstrates a Differential Chaperone Activity of Calf α-Crystallin toward βLOW- and Individual γ-Crystallins

Putilina¹,

Skouri‐Panet²,

Prat³

et al. 2003

Journal of Biological Chemistry

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The chaperone activity of native ␣-crystallins toward ␤ LOW -and various ␥-crystallins at the onset of their denaturation, 60 and 66°C, respectively, was studied at high and low crystallin concentrations using small angle x-ray scattering (SAXS) and fluorescence energy transfer (FRET). The crystallins were from calf lenses except for one recombinant human ␥S. SAXS data demonstrated an irreversible doubling in molecular weight and a corresponding increase in size of ␣-crystallins at temperatures above 60°C. Further increase is observed at 66°C. More subtle conformational changes accompanied the increase in size as shown by changes in environments around tryptophan and cysteine residues. These ␣-crystallin temperature-induced modifications were found necessary to allow for the association with ␤ LOW -and ␥-crystallins to occur. FRET experiments using IAEDANS (iodoacetylaminoethylaminonaphthalene sulfonic acid)-and IAF (iodoacetamidofluorescein)-labeled subunits showed that the heat-modified ␣-crystallins retained their ability to exchange subunits and that, at 37°C, the rate of exchange was increased depending upon the temperature of incubation, 60 or 66°C. Association with ␤ LOW -(60°C) or various ␥-crystallins (66°C) resulted at 37°C in decreased subunit exchange in proportion to bound ligands. Therefore, ␤ LOW -and ␥-crystallins were compared for their capacity to associate with ␣-crystallins and inhibit subunit exchange. Quite unexpectedly for a highly conserved protein family, differences were observed between the individual ␥-crystallin family members. The strongest effect was observed for ␥S, followed by h␥Srec, ␥E, ␥A-F, ␥D, ␥B. Moreover, fluorescence properties of ␣-crystallins in the presence of bound ␤ LOW -and ␥-crystallins indicated that the formation of ␤ LOW /␣-or ␥/␣-crystallin complexes involved various binding sites. The changes in subunit exchange associated with the chaperone properties of ␣-crystallins toward the other lens crystallins demonstrate the dynamic character of the heat-activated ␣-crystallin structure.␣-Crystallins and small heat shock proteins have in common a conserved C-terminal domain of about 115 residues, the ␣-crystallin domain, the structure of which is organized around an eight-stranded ␤-sandwich (1, 2). The small heat shock proteins usually associate into high molecular weight monodisperse or polydisperse oligomers, able to protect against stress through the binding of a variety of partially unfolded substrates. ␣-Crystallin was demonstrated by Horwitz in 1992 (3) to also exhibit chaperone properties in vitro. It is able to bind ␤-and ␥-crystallins at the onset of their thermal denaturation, thus preventing further denaturation and aggregation, yet not refolding. Following this pioneering work, the chaperone-like activity of ␣-crystallin has been the subject of numerous studies and functional models have been suggested (4 -30). Essentially, hydrophobic patches on the surface, either present in the native state or revealed after structural modifications, would associate w...

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“…It is evident that the ␣-crystallin-type proteins that are induced in response to stimuli other than heat stress must act differently from Hsp26. Many ␣-Hsps function as efficient chaperones not only on thermally but also on chemically denatured substrates at low temperatures in vitro (e.g., on dithiothreitol [DTT]-treated insulin) (1,188,253). While temperature-mediated dissociation of ␣-Hsps might not be a universal phenomenon, more subtle temperature effects on the structural properties, chaperone activity, and subunit exchange of various family members are common.…”

Section: Plasticity Of Oligomer Formationmentioning

confidence: 99%

α-Crystallin-Type Heat Shock Proteins: Socializing Minichaperones in the Context of a Multichaperone Network

Narberhaus

2002

Microbiol Mol Biol Rev

491

415

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SUMMARY α-Crystallins were originally recognized as proteins contributing to the transparency of the mammalian eye lens. Subsequently, they have been found in many, but not all, members of the Archaea, Bacteria, and Eucarya. Most members of the diverse α-crystallin family have four common structural and functional features: (i) a small monomeric molecular mass between 12 and 43 kDa; (ii) the formation of large oligomeric complexes; (iii) the presence of a moderately conserved central region, the so-called α-crystallin domain; and (iv) molecular chaperone activity. Since α-crystallins are induced by a temperature upshift in many organisms, they are often referred to as small heat shock proteins (sHsps) or, more accurately, α-Hsps. α-Crystallins are integrated into a highly flexible and synergistic multichaperone network evolved to secure protein quality control in the cell. Their chaperone activity is limited to the binding of unfolding intermediates in order to protect them from irreversible aggregation. Productive release and refolding of captured proteins into the native state requires close cooperation with other cellular chaperones. In addition, α-Hsps seem to play an important role in membrane stabilization. The review compiles information on the abundance, sequence conservation, regulation, structure, and function of α-Hsps with an emphasis on the microbial members of this chaperone family.

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Chaperone-like Activity of Bovine Lens α-Crystallin in the Presence of Dithiothreitol-Destabilized Proteins: Characterization of the Formed Complexes

Cited by 20 publications

References 17 publications

On the Equilibrium between Monomeric α-Lactalbumin and the Chaperoning Complex of α-Crystallin

On the Equilibrium between Monomeric α-Lactalbumin and the Chaperoning Complex of α-Crystallin

Subunit Exchange Demonstrates a Differential Chaperone Activity of Calf α-Crystallin toward βLOW- and Individual γ-Crystallins

α-Crystallin-Type Heat Shock Proteins: Socializing Minichaperones in the Context of a Multichaperone Network

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