The structure and oxidation of the eye lens chaperone αA-crystallin

Christoph J.O. Kaiser, Carsten Peters, Philipp W.N. Schmid, Maria Stavropoulou, Juan Zou, Vinay Dahiya, Evgeny V. Mymrikov, Beate Rockel, Sam Asami, Martin Haslbeck, Juri Rappsilber, Bernd Reif, Martin Zacharias, Johannes Buchner, Sevil Weinkauf

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The small heat shock protein αA-crystallin is a molecular chaperone important for the optical properties of the vertebrate eye lens. It forms heterogeneous oligomeric ensembles. We determined the structures of human αA-crystallin oligomers by combining cryo-electron microscopy, cross-linking/mass spectrometry, NMR spectroscopy and molecular modeling. The different oligomers can be interconverted by the addition or subtraction of tetramers, leading to mainly 12-, 16- and 20-meric assemblies in which interactions between N-terminal regions are important. Cross-dimer domain-swapping of the C-terminal region is a determinant of αA-crystallin heterogeneity. Human αA-crystallin contains two cysteines, which can form an intramolecular disulfide in vivo. Oxidation in vitro requires conformational changes and oligomer dissociation. The oxidized oligomers, which are larger than reduced αA-crystallin and destabilized against unfolding, are active chaperones and can transfer the disulfide to destabilized substrate proteins. The insight into the structure and function of αA-crystallin provides a basis for understanding its role in the eye lens.

Original languageEnglish
Pages (from-to)1141-1150
Number of pages10
JournalNature Structural and Molecular Biology
Issue number12
StatePublished - 1 Dec 2019


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