High-molecular-weight protein aggregates of calf and cow lens: Spectroscopic evaluation

Messmer, Marie C.; Chakrabarti, Buddhapriya

doi:10.1016/0014-4835(88)90001-2

Cited by 17 publications

(6 citation statements)

References 29 publications

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“…HMW ␣-crystallin observed earlier (16,19). The decreased intensity in the whole near-UV region was also reported earlier for bovine HMW ␣-crystallin (18,20). In human HMW ␣-crystallin, the decrease is particularly prominent between 270 and 290 nm.…”

Section: Figsupporting

confidence: 76%

Human Lens High-Molecular-Weight α-Crystallin Aggregates

Liang

Akhtar

2000

Biochemical and Biophysical Research Communications

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Section: Figsupporting

confidence: 76%

Human Lens High-Molecular-Weight α-Crystallin Aggregates

Liang

Akhtar

2000

Biochemical and Biophysical Research Communications

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“…2), the relatively hydrophobic N-terminal domain does not undergo any gross conformational changes upon complexation although there is some increase in polarity of the environment of the tryptophan residues upon HMM formation with the insulin B chain. The naturally occurring HMM complex from older lenses also has increased polarity of its N-terminal tryptophan residues compared to A-crystallin of the same age [46], suggesting that this species may have arisen from chaperone action within the lens. The 31 P-NMR spectra of A-crystallin and AA-crystallin imply that there is little alteration in the environment of the various phosphorylated serine residues upon HMM formation with the insulin B chain (Fig.…”

Section: Discussionmentioning

confidence: 99%

Structural alterations of α‐crystallin during its chaperone action

Lindner

Kapur

Mariani

et al. 1998

European Journal of Biochemistry

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The small heat-shock protein, A-crystallin, has chaperone ability whereby it stabilises proteins under stress conditions. In this study, alterations in the structure of A-crystallin during its interaction with a variety of substrate proteins (insulin, A-lactalbumin, ovotransferrin and serum albumin) under stress conditions have been examined using visible absorption, 31 P-NMR and 1 H-NMR and fluorescence spectroscopy. The fluorescence and 31 P-NMR data imply that during the chaperone action of A-crystallin under reducing conditions, there is a slight increase in hydrophilicity of its N-terminal region and an alteration in flexibility of its C-terminal region, but overall, A-crystallin does not undergo a gross structural change. The fluorescence data suggest that substrate proteins interact with A-crystallin in a molten globule or intermediately folded state. The same conclusion is made from 1 H-NMR spectroscopic monitoring of the interaction of A-crystallin with substrate proteins, e.g. the insulin B chain. The stoichiometry of interaction between A-crystallin and the various substrate proteins reveals that steric factors are important in determining the efficiency of interaction between the two proteins, i.e. on a molar subunit basis, A-crystallin is a more efficient chaperone protein with smaller substrate proteins. Comparison is also made between the high-molecular-mass (HMM) complexes formed between A-crystallin and ovotransferrin when reduced and heat stressed. Under heating conditions, fluorescence spectroscopy indicates that the HMM complex has a greater exposure of hydrophobicity to solution than that formed by reduction. Furthermore, in interacting with heated ovotransferrin, the C-terminal extension of the AB-crystallin subunit preferentially loses its flexibility suggesting that it is involved in stabilising bound ovotransferrin. By contrast, this extension is only partially reduced in flexibility in the HMM complex formed after reduction of ovotransferrin. The functional role of the C-terminal extensions in the chaperone action and the overall quaternary structure of A-crystallin is discussed.

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“…In fact, thermal as well as sugar-induced aggregation (Liang & Chakrabarti, 1981) is followed by a drastic change in the tertiary structure of these crystallins. In aging and cataractogenesis, the formation of high molecular weight components and increased insolubilization of crystallins may not be a consequence of complete denaturation (random structure) of proteins, as suggested (Harding & Dilley, 1976), but in most cases, they are preceded by a change in the tertiary structure (Messmer & Chakrabarti, 1988).…”

Section: Discussionmentioning

confidence: 99%

Thermodynamics of thermal and athermal denaturation of .gamma.-crystallins: changes in conformational stability upon glutathione reaction

Kono

Sen²,

Chakrabarti³

1990

Biochemistry

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The conformational stabilities of bovine lens gamma-crystallin fractions II, IIIA, IIIB, and IVA and those modified with glutathione were compared by studying the thermal and guanidine hydrochloride (Gdn-HCl) denaturation behavior. The conformational state was monitored by both far-UV CD and fluorescence measurements. All the gamma-crystallins studied showed a sigmoidal order-disorder transition with varied melting temperatures. The thermal denaturation of these proteins is reversible up to a temperature 3 or 4 degrees C above T 1/2; above this temperature, irreversible aggregation occurs. The validity of a two-state approximation of both thermal and Gdn-HCl denaturation was tested for all four crystallins, and the presence of one or more intermediates was evident in the unfolding of IVA. delta GDH2O values of these crystallins range from 4 to 9 kcal/mol. Upon glutathione treatment IVA showed the maximum decrease in T 1/2 by approximately 9 degrees C and in delta GDH2O value by 29%; the smallest decrease in T 1/2 was for IIIA by 2 degrees C and in delta GDH2O by 15%. We have demonstrated that the glutathione reaction can dramatically reduce the conformational stability of gamma-crystallins and, thus, that the thermodynamic quantities of the unreacted crystallins can be used to evaluate the stability of these proteins when modified during cataract formation.

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High-molecular-weight protein aggregates of calf and cow lens: Spectroscopic evaluation

Cited by 17 publications

References 29 publications

Human Lens High-Molecular-Weight α-Crystallin Aggregates

Human Lens High-Molecular-Weight α-Crystallin Aggregates

Structural alterations of α‐crystallin during its chaperone action

Thermodynamics of thermal and athermal denaturation of .gamma.-crystallins: changes in conformational stability upon glutathione reaction

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