Acta Crystallographica Section D

Biological Crystallography

Volume 69, Part 6 (June 2013)

research papers

Acta Cryst. (2013). D69, 960-967    [ doi:10.1107/S0907444913003569 ]

A novel interdomain interface in crystallins: structural characterization of the [beta][gamma]-crystallin from Geodia cydonium at 0.99 Å resolution

A. Vergara, M. Grassi, F. Sica, E. Pizzo, G. D'Alessio, L. Mazzarella and A. Merlino

Abstract: The [beta][gamma]-crystallin superfamily includes highly diverse proteins belonging to all of the kingdoms of life. Based on structural topology, these proteins are considered to be evolutionarily related to the long-lived [beta][gamma]-crystallins that constitute the vertebrate eye lens. This study reports the crystallographic structure at 0.99 Å resolution of the two-domain [beta][gamma]-crystallin (geodin) from the sponge Geodia cydonium. This is the most ancient member of the [beta][gamma]-crystallin superfamily in metazoans. The X-ray structure shows that the geodin domains adopt the typical [beta][gamma]-crystallin fold with a paired Greek-key motif, thus confirming the hypothesis that the crystallin-type scaffold used in the evolution of bacteria and moulds was recruited very early in metazoans. As a significant new structural feature, the sponge protein possesses a unique interdomain interface made up by pairing between the second motif of the first domain and the first motif of the second domain. The atomic resolution also allowed a detailed analysis of the calcium-binding site of the protein.

PDB reference: 4iau

Keywords: crystallins; atomic resolution; calcium binding; domain interactions; folding; Greek-key motif; Tyr corner; Trp corner.

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[ doi:10.1107/S0907444913003569/lv5035sup1.pdf ]
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