Benefits of being heteromers: γ-crystallin heteromer is more stable than the homomers during thermal denaturation

【作者】 冷筱瑶； 闫永彬；

【机构】 State Key Laboratory of Biomembrane and Membrane Biotechnology,School of Life Sciences, Tsinghua University；

【摘要】 α-,β-andγ-crystallins are the major protein components in human lens.α-Crystallinserves as a molecular chaperone,whileβ-andγ-crystallins are the main structural proteinsin the lens.The solubility and stability of crystallins are important in maintaining the transparencyand refraction index of lens.When subject to the persistent environmentalstresses during aging,crystallins may lose their solubility and stability.The aggregation ofcrystallins will interfere with the vision by scattering of the light,which is generally recognizedas the main cause of aging cataract.In the lens,β-crystallins exist as heteromers with 2-8 subunits using the basic and acidicβ-crystallins as the building blocks.The basicβ-crystallin is generally more stable than acidicβ-crystallin.Our previous research has shown that the basicβ-crystallin could protect theacidicβ-crystallin against aggregation during refolding and denaturation.In this research,we further investigated the sequential events in the thermal denaturation ofβA3-crystallinhomomer,βB1-crystallin homomer andβA3/βB1-crystallin heteromer by a combination ofspectroscopic methods.The results showed thatβA3/βB1 heteromer was the most stableamong the three proteins,whileβA3-crystallin is the most aggregation-prone.DSC experimentsconfirmed that the Tm ofβA3-crystallin is much lower than those of the other twoproteins.These results suggested that the formation ofβ-crystallin heteromers not onlystabilized the unstable acidicβ-crystallins,but also improve the stability of the basicβ-crystallins.These findings provide insight into the molecular basis of whyβ-crystallins existas heteromers in vivo,and may be important to the understanding of the onset of cataractcaused byβ-crystallin aggregation.更多还原

【Abstract】 α-,β-andγ-crystallins are the major protein components in human lens.α-Crystallinserves as a molecular chaperone,whileβ-andγ-crystallins are the main structural proteinsin the lens.The solubility and stability of crystallins are important in maintaining the transparencyand refraction index of lens.When subject to the persistent environmentalstresses during aging,crystallins may lose their solubility and stability.The aggregation ofcrystallins will interfere with the vision by scattering of the light,which is generally recognizedas the main cause of aging cataract.In the lens,β-crystallins exist as heteromers with 2-8 subunits using the basic and acidicβ-crystallins as the building blocks.The basicβ-crystallin is generally more stable than acidicβ-crystallin.Our previous research has shown that the basicβ-crystallin could protect theacidicβ-crystallin against aggregation during refolding and denaturation.In this research,we further investigated the sequential events in the thermal denaturation ofβA3-crystallinhomomer,βB1-crystallin homomer andβA3/βB1-crystallin heteromer by a combination ofspectroscopic methods.The results showed thatβA3/βB1 heteromer was the most stableamong the three proteins,whileβA3-crystallin is the most aggregation-prone.DSC experimentsconfirmed that the Tm ofβA3-crystallin is much lower than those of the other twoproteins.These results suggested that the formation ofβ-crystallin heteromers not onlystabilized the unstable acidicβ-crystallins,but also improve the stability of the basicβ-crystallins.These findings provide insight into the molecular basis of whyβ-crystallins existas heteromers in vivo,and may be important to the understanding of the onset of cataractcaused byβ-crystallin aggregation.更多还原