A Test for Stabilization of an Oligomeric Protein by Introduction of Aromatic Residues into the Interface

The design of variants to enhance conformational stability of proteins is an important aspect of protein engineering. Oligomeric proteins are often stabilized by aromatic clusters located within the subunit interfaces. In the present study, the authors constructed five variants of Ps3αHSD (Pseudomonas sp. B-0831 3-hydroxysteroid dehydrogenase) in which one or two residues at the dimer interface were replaced with aromatic residues, and examined the effects of introducing aromatic residues in this region on protein thermostability. Under their experimental conditions, all variants formed dimers, similar to wild-type Ps3αHSD. Thermal denaturation experiments indicated that Tm of all variants was 0.2-16.2 oC lower than that of wild-type protein, indicating less stable thanwild-type protein. The results collectively suggest that aromatic residues of natural oligomeric proteins are strictly posted in the interface to facilitate optimal interactions and avoid conformational strain.