Crystal structure of a dimerization domain of Drosophila Caprin protein

The Drosophila Melanogaster Caprin protein (dCaprin), as well as the human Caprin‐1 and Caprin‐2 proteins, are prototypic members of the caprin (cytoplasmic activation/proliferation‐associated protein) protein family. Caprin proteins contain two highly conserved homologous regions (HR1 and HR2) and C‐terminal RGG motifs characteristic of RNA‐binding proteins. The detailed molecular mechanisms of caprin protein functions remain largely unknown. We had previously determined the crystal structure of a ~120‐residue fragment of Caprin‐1 and Caprin‐2 within the HR1 region. Here, we report the determination of the crystal structure of a corresponding fragment in dCaprin. Our structural studies show that all three structures of dCaprin, Caprin‐1, and Caprin‐2 have a similar novel all α‐helical fold that self‐associates to form a homodimer. Structural comparison reveals that the molecular interactions mediating homodimerization of the three proteins are largely conserved in the three systems. Presence of a dimerization domain within HR1 may represent an evolutionarily conserved feature of the caprin protein family. Interestingly, while the caprin proteins adopt similar overall dimeric structures, the structures have quite different molecular surface properties. The different surface properties of the caprin dimeric structures may dictate their intermolecular interaction with specific protein partners. Support or Funding Information SIUC Seed Grant This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .