Molecule of the Month: Crystallins
A concentrated solution of crystallins refracts light in our eye lens
![Different forms of crystallin proteins.](https://cdn.rcsb.org/pdb101/motm/127/mom127_crystallins2.jpg)
Crystal Clear
Transparency Through Diversity
Moonlighting Proteins
Cataracts
Exploring the Structure
Beta and Gamma Crystallin (PDB entries 1blb and 4gcr)
![](https://cdn.rcsb.org/pdb101/motm/127/mom127_1blb_jmol.jpg)
The key to crystallin function is their ability to form many different types of similar complexes, so that they will form a smooth, random arrangement when concentrated inside lens cells. The crystal structures of crystallins have revealed that they use domain swapping to form many different complexes using a small number of building blocks. Beta crystallin uses a classic domain swapping mechanism to mix-and-match different variants of the beta chain, and alpha crystallins use a more complex mechanism to create larger complexes. Click the images above to see Jmols that show these domain swaps in detail.
Topics for Further Discussion
- Many proteins use domain swapping to create stable complexes. Can you find other examples in the PDB? (Hint: many researchers mention the term "domain swapping" in their titles or abstracts).
- Can you think of any other proteins with two or more different functions?
Related PDB-101 Resources
- Browse You and Your Health
- Browse Biomolecules
References
- K. K. Sharma and P. Santhoshkumar (2009) Lens aging: effects of crystallins. Biochimica et Biophysica Acta 1790, 1095-1108.
- L. Takemoto and C. M. Sorensen (2008) Protein-protein interactions and lens transparency. Experimental Eye Research 87, 496-501.
- H. Bloemendal, W. de Jong, R. Jaenicke, N. H. Lubsen, C. Slingsby and A. Tardieu (2004) Ageing and vision: structure, stability and function of lens crystallins. Progress in Biophysics and Molecular Biology 86, 407-485.
July 2010, David Goodsell
http://doi.org/10.2210/rcsb_pdb/mom_2010_7