α‐Crystallin prevents irreversible protein denaturation and acts cooperatively with other heat‐shock proteins to renature the stabilized partially denatured protein in an ATP‐dependent manner
2000; Wiley; Volume: 267; Issue: 15 Linguagem: Inglês
10.1046/j.1432-1327.2000.01521.x
ISSN1432-1033
Autores Tópico(s)Yersinia bacterium, plague, ectoparasites research
Resumoα‐Crystallin, a major lens protein of ≈ 800 kDa with subunits of ≈ 20 kDa has previously been shown to act as a chaperone protecting other proteins from stress‐induced aggregation. Here it is demonstrated that α‐crystallin can bind to partially denatured enzymes at 42–43 °C and prevent their irreversible aggregation, but cannot prevent loss of enzyme activity. However, the α‐crystallin‐bound enzymes regain activity on interaction with other chaperones. The data indicate that the re‐activated enzymes are no longer associated with the α‐crystallin, and ATP is required for re‐activation. When inactive luciferase bound to α‐crystallin was treated with reticulocyte lysate, a rich source of chaperones, up to 60% of the original luciferase activity could be recovered. Somewhat less re‐activation was observed when the α‐crystallin‐bound enzyme was treated with heat‐shock protein (HSP)70, HSP40, HSP60 and an ATP‐generating system. Similar results were also obtained with citrate synthase. The overall results suggest that α‐crystallin acts to stabilize denaturing proteins so that they can later be re‐activated by other chaperones.
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