Specificity of αA‐crystallin binding to destabilized mutants of βB1‐crystallin

Mchaourab, Hassane S.; Kumar, Mukesh; Koteiche, Hanane A.

doi:10.1016/j.febslet.2007.04.005

Cited by 20 publications

(21 citation statements)

References 21 publications

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“…When β -crystallins are partially unfolded during urea-denaturation (McHaourab et al, 2007; Moreau and King, 2012; Sathish et al, 2004) or thermal-denaturation (Lampi et al, 2012; McHaourab et al, 2007; Moreau and King, 2012; Sathish et al, 2004; Takata et al, 2009), they form a complex with α -crystallin, similar to what has been reported between α -crystallin and γ -crystallins (Acosta-Sampson and King, 2010). However, α -crystallin is not able to completely rescue deamidated β -crystallins from heat-induced precipitation (Lampi et al, 2002a; Michiel et al, 2010) (Fig.…”

Section: The Effect Of Deamidation On β-Crystallin Structure and Ssupporting

confidence: 53%

Lens β-crystallins: The role of deamidation and related modifications in aging and cataract

Lampi¹,

Wilmarth²,

Murray³

et al. 2014

Progress in Biophysics and Molecular Biology

126

117

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Crystallins are the major proteins in the lens of the eye and function to maintain transparency of the lens. Of the human crystallins, α, β, and γ, the β-crystallins remain the most elusive in their structural significance due to their greater number of subunits and possible oligomer formations. The β-crystallins are also heavily modified during aging. This review focuses on the functional significance of deamidation and the related modifications of racemization and isomerization, the major modifications in β-crystallins of the aged human lens. Elucidating the role of these modifications in cataract formation has been slow, because they are analytically among the most difficult post-translational modifications to study. Recent results suggest that many amides deamidate to similar extent in normal aged and cataractous lenses, while others may undergo greater deamidation in cataract. Mimicking deamidation at critical structural regions induces structural changes that disrupt the stability of the β-crystallins and lead to their aggregation in vitro. Deamidations at the surface disrupt interactions with other crystallins. Additionally, the α-crystallin chaperone is unable to completely prevent deamidated β-crystallins from insolubilization. Therefore, deamidation of β-crystallins may enhance their precipitation and light scattering in vivo contributing to cataract formation. Future experiments are needed to quantify differences in deamidation rates at all Asn and Gln residues within crystallins from aged and cataractous lenses, as well as racemization and isomerization which potentially perturb protein structure greater than deamidation alone. Quantitative data is greatly needed to investigate the importance of these major age-related modifications in cataract formation.

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Section: The Effect Of Deamidation On β-Crystallin Structure and Ssupporting

confidence: 53%

Lens β-crystallins: The role of deamidation and related modifications in aging and cataract

Lampi¹,

Wilmarth²,

Murray³

et al. 2014

Progress in Biophysics and Molecular Biology

126

117

View full text Add to dashboard Cite

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“…Apparent dissociation constants of T4L binding to α-crystallin are at least an order of magnitude smaller than those measured for the most destabilized γD-crystallin mutant investigated here, I4F/V76D [28,40]. Weak affinities to α-crystallin were also observed for βB1-crystallin mutants and attributed to the population of a dimeric intermediate with low affinity to α-crystallin [41]. Together, these results suggest that interaction between lens proteins and α-crystallin in the “chaperone mode” departs from the mechanistic principles deduced from studies of model substrates.…”

Section: Discussionmentioning

confidence: 88%

Cataract‐linked γD‐crystallin mutants have weak affinity to lens chaperones α‐crystallins

Mishra¹,

Stein²,

Mchaourab³

2012

FEBS Letters

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To test the hypothesis that α-crystallin chaperone activity plays a central role in maintenance of lens transparency, we investigated its interactions with γ-crystallin mutants that cause congenital cataract in mouse models. Although the two substitutions, I4F and V76D, stabilize a partially unfolded γD-crystallin intermediate, their affinities to α-crystallin are marginal even at relatively high concentrations. Detectable binding required further reduction of γD-crystallin stability which was achieved by combining the two mutations. Our results demonstrate that mutants and possibly age-damaged γ-crystallin can escape quality control by lens chaperones rationalizing the observation that they nucleate protein aggregation and lead to cataract.

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“…35 Because dissociation and unfolding of βB1-crystallin are coupled, 36 this result implies that the bound conformation is likely to be extensively unfolded.…”

Section: Discussionmentioning

confidence: 95%

Structure and Orientation of T4 Lysozyme Bound to the Small Heat Shock Protein α-Crystallin

Claxton

Zou

Mchaourab

2008

Journal of Molecular Biology

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We have determined the structural changes that accompany the formation of a stable complex between a destabilized mutant of T4 lysozyme (T4L) and the small heat shock protein alpha-crystallin. Using pairs of fluorescence or spin label probes to fingerprint the T4L tertiary fold, we demonstrate that binding disrupts tertiary packing in the two domains as well as across the active-site cleft. Furthermore, increased distances between i and i+4 residues of helices support a model in which the bound structure is not native-like but significantly unfolded. In the confines of the oligomer, T4L has a preferential orientation with residues in the more hydrophobic C-terminal domain sequestered in a buried environment, while residues in the N-terminal domain are exposed to the aqueous solvent. Furthermore, electron paramagnetic resonance spectral line shapes of sites in the N-terminal domain are narrower than in the folded, unbound T4L reflecting an unstructured backbone and an asymmetric pattern of contacts between T4L and alpha-crystallin. The net orientation is not affected by the location of the destabilizing mutation consistent with the notion that binding is not triggered by recognition of localized unfolding. Together, the structural and thermodynamic data indicate that the stably bound conformation of T4L is unfolded and support a model in which the two modes of substrate binding originate from two discrete binding sites on the chaperone.

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Specificity of αA‐crystallin binding to destabilized mutants of βB1‐crystallin

Cited by 20 publications

References 21 publications

Lens β-crystallins: The role of deamidation and related modifications in aging and cataract

Lens β-crystallins: The role of deamidation and related modifications in aging and cataract

Cataract‐linked γD‐crystallin mutants have weak affinity to lens chaperones α‐crystallins

Structure and Orientation of T4 Lysozyme Bound to the Small Heat Shock Protein α-Crystallin

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