Suppression of DTT‐induced aggregation of abrin by αA‐ and αB‐crystallins: a model aggregation assay for α‐crystallin chaperone activity in vitro 1

FEBS Letters

Narayanan, Sriram¹  Surolia, Ira¹  Reddy, G.Bhanuprakash²  Reddy, P.Yadagiri² 

[1] Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India;Biochemistry Division, National Institute of Nutrition, Hyderabad 500 007, India

关键词: α-Crystallin;    Heat shock protein-26;    Abrin;    Insulin;    Molecular chaperone;    Small heat shock protein;    Hydrophobicity;    Gel filtration;    DTT;    dithiothreitol;    PBS;    phosphate-buffered saline;    sHSP;    small heat shock protein;   

DOI  :  10.1016/S0014-5793(02)02884-3

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The eye lens small heat shock proteins (sHSP), αA- and αB-crystallins, have been shown to function like molecular chaperones, both in vitro and in vivo. It is essential to assess the protective effect of αA- and αB-crystallins under native conditions to extrapolate the results to in vivo conditions. Insulin and α-lactalbumin have widely been used to investigate the chaperone mechanism of α-crystallin under native conditions. Due to its smaller size, insulin B-chain may not represent the binding of putative physiological substrate proteins. As it stands, the aggregation of α-lactalbumin and binding of α-crystallin to it varies under different experimental conditions. Abrin, a ribosome inactivating protein isolated from the seeds of Abrus precatorius, consists of a 30 kDa A-chain and a lectin-like B-chain of 33 kDa joined by a single disulfide bond. Reduction of the disulfide link between the two chains of abrin leads to the aggregation of the B-chain. In this study, we demonstrate that dithiothreitol (DTT)-induced aggregation of abrin B-chain could be monitored by light scattering similar to that of insulin. Moreso, this process could be suppressed by recombinant human αA- and αB-crystallins in a concentration dependent manner, notably by binding to aggregation prone abrin B-chain. SDS–PAGE and HPLC gel filtration analysis indicate that there is a soluble complex formation between α-crystallin and abrin B-chain. Interestingly, in contrast to insulin, there is no significant difference between αA- and αB-crystallin in suppressing the aggregation of abrin B-chain at two different temperatures (25 and 37°C). HSP26, an another small heat shock/α-crystallin family protein, was also able to prevent the DTT-induced aggregation of abrin. These results suggest that due to relatively larger size of its B-chain (33 kDa), compared to insulin B-chain (about 3 kDa), abrin may serve as a better model substrate for in vitro chaperone studies of α-crystallin and as well as other sHSP.

【 授权许可】

Unknown