Specificity of alpha crystallin binding to the lens membrane

Ifeanyi, F.; Takemoto, L.

doi:10.3109/02713689009044521

Cited by 43 publications

(20 citation statements)

References 13 publications

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“…2). These observations are in contrast to previous reports that suggested that ␣A-crystallin but not ␣B-crystallin was the only subunit involved with membrane association (20,23). Our results also show that this interaction is sensitive to time and temperature, FIG.…”

Section: Discussioncontrasting

confidence: 57%

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Characterization of α-Crystallin-Plasma Membrane Binding

Cobb¹,

Petrash²

2000

Journal of Biological Chemistry

113

115

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␣-Crystallin, a large lenticular protein complex made up of two related subunits (␣A-and ␣B-crystallin), is known to associate increasingly with fiber cell plasma membranes with age and/or the onset of cataract. To understand better the binding mechanism, we developed a sensitive membrane binding assay using lens plasma membranes and recombinant human ␣A-and ␣B-crystallins conjugated to a small fluorescent tag (Alexa350 ® ). Both ␣A and ␣B homopolymer complexes, as well as a reconstituted 3:1 heteromeric complex, bind to lens membranes in a specific, saturable, and partially irreversible manner that is sensitive to both time and temperature. The amount of ␣-crystallin that binds to the membrane increases under acidic pH conditions and upon removal of exposed intrinsic membrane protein domains but is not affected at high ionic strength, suggesting that ␣-crystallin binds to the fiber cell plasma membranes mainly through hydrophobic interactions. The binding capacity and affinity for the reconstituted 3:1 heteromeric complex were measured to be 3.45 ؎ 0.11 ng/g of membrane and 4.57 ؎ 0.50 ؋ 10 ؊4 g ؊1 of membrane, respectively. The present membrane binding data support the hypothesis that the physical properties of a mixed ␣-crystallin complex may hold particular relevance for the function of ␣-crystallin within the lens.

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Section: Discussioncontrasting

confidence: 57%

“…In addition, saturable binding to protein-free phospholipid vesicles has been observed, but the measured capacity is reduced dramatically upon incorporation of cholesterol (31)(32)(33). Finally, it has been postulated that ␣B-crystallin is largely unable to bind membranes in the absence of ␣A-crystallin (20,23).…”

mentioning

confidence: 93%

Characterization of α-Crystallin-Plasma Membrane Binding

Cobb¹,

Petrash²

2000

Journal of Biological Chemistry

113

115

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“…Historically, a fraction of ␣-crystallin (both ␣A and ␣B) has been reported to be membrane-associated in the normal adult transparent lens. These observations about the association of ␣-crystallins with the membranes were first made about four decades ago (32)(33)(34)(35). We therefore examined ␣A status first in the lens epithelial explants in culture and then in the early developing lens.…”

Section: Discussionmentioning

confidence: 99%

αA-Crystallin and αB-Crystallin Reside in Separate Subcellular Compartments in the Developing Ocular Lens

Gangalum

Horwitz

Kohan

et al. 2012

Journal of Biological Chemistry

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Background:The small heat shock proteins, ␣A-crystallin and ␣B-crystallin are considered to be two subunits of one single monolithic lens protein, ␣-crystallin. Results: ␣A-Crystallin and ␣B-crystallin fractionate independent of each other and in two separate membrane compartments. Conclusion: ␣A-Crystallin and ␣B-crystallin are two independent proteins in the lens. Significance: These data provide functional insight into why ␣A-crystallin and ␣B-crystallin null mice have disparate phenotypes.

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“…It had been thought to be a lens specific, structural protein until a few years ago. Identification of this protein in several non-lenticular tissues such as heart, muscle and kidney [14] suggests that it might have a role to play in other functions. It is structurally related to small heat-shock proteins (Hsps), behaves in several ways like Hsps [5][6][7][8] and its expression can be induced by thermal [5] and osmotic stress [9].…”

Section: Introductionmentioning

confidence: 99%

“…It is structurally related to small heat-shock proteins (Hsps), behaves in several ways like Hsps [5][6][7][8] and its expression can be induced by thermal [5] and osmotic stress [9]. Like some Hsps [1(~12] it is known to interact with membranes [13,14], cytoskeletal elements [15,16], and to modulate the intermediate filament assembly [17]. Mixed assemblies of ~B and some Hsps have been observed both in vivo [18,19] and in vitro [8].…”

Section: Introductionmentioning

confidence: 99%

Temperature dependent chaperone‐like activity of alpha‐crystallin

1995

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Alpha-crystallin, a multimeric protein present in the eye lens, is known to have chaperone-like activity in preventing the aggregation of enzymes and other crystallins. We have studied the chaperone-like activity of this protein towards the aggregation of insulin B chain, induced by reducing the interchain disulphide bond with dithiothreitol. At room temperature, there is no detectable protection (at a I:I (wlw) ratio of insulin: txcrystallin) against the aggregation of insulin B chain by ot-crystallin, whereas it completely prevents this aggregation at 40 ° C. We have monitored the temperature dependence of the protection of aggregation by a-crystallin; the protection increases sharply above 30°C and reaches almost 100% by 41°C. Probing the hydrophobic surfaces of a-crystallin with the hydrophobic fluorphore 8-anilino-I naphthalene sulfonate suggests that the hydrophobic surfaces of a-crystallin are exposed to a greater extent above 30°C. A complete prevention of the aggregation is achieved at 27.6°C by increasing the concentration of a-crystallin by more than 8 fold. Similar temperature dependent chaperone-like activity of a-crystallin is observed towards the aggregation of zetacrystallin, an enzyme crystallin from guinea pig. We have earlier shown that a-crystallin exposes hydrophobic surface(s) at temperatures above 30°C. These results support our earlier hypothesis [Raman, B. and Rao, Ch.M. (1994) J. Biol. Chem. 269, 27264-27268] that the chaperone-like activity of ot-crystallin is more pronounced in its structurally perturbed state.

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Specificity of alpha crystallin binding to the lens membrane

Cited by 43 publications

References 13 publications

Characterization of α-Crystallin-Plasma Membrane Binding

Characterization of α-Crystallin-Plasma Membrane Binding

αA-Crystallin and αB-Crystallin Reside in Separate Subcellular Compartments in the Developing Ocular Lens

Temperature dependent chaperone‐like activity of alpha‐crystallin

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