摘要
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 angstrom 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.
- 出版日期2013-6