Molecule of the Month: Legumain
Legumain cleaves proteins, and can also put them back together.
Cutting and Pasting
Exploring the Structure
PDB entry 4awb captures legumain in the middle of its reaction. At top left, a short peptide has been cleaved and half is left attached to the catalytic cysteine. Later, a water molecule will be used to release the attached peptide. PDB entry 4n6o shows legumain bound to the inhibitory protein cystatin. As seen at bottom left, it also has an asparagine that fits into the specificity pocket, but it is cleaved very slowly, and when cleaved, it is also reconnected by legumain. The images on the right show an aspartate that adopts an unusual aminosuccinimide form that is thought to be important in the ligation reaction. Click on the image to explore the structure, and display the amino acids in the specificity pocket and the modified aspartate.
Topics for Further Discussion
- Try comparing the structures of legumain (4awb) and caspase 1 (2hbq).
- Several other proteins have the unusual aminosuccinimide form of aspartate. You can find a listing of examples at the Ligand Depot page for SNN.
August 2018, David Goodsellhttp://doi.org/10.2210/rcsb_pdb/mom_2018_8