UbiquitinPDB ID: 1UBQ
A chain of ubiquitin molecules are added to obsolete proteins, indicating that they need to be destroyed. This structure includes a single ubiquitin molecule.
Structure of ubiquitin refined at 1.8 A resolution.
Vijay-Kumar, S., Bugg, C.E., Cook, W.J.
Journal: (1987) J.Mol.Biol. 194: 531-544