Proteins with the double stranded beta-helix (DSBH, also known as cupin) fold perform a diverse range of functions. In this study, Bacillus subtilis quercetinase was used as a model system to understand the conformational determinants of functional diversity within the cupin fold. Controlled proteolysis experiments revealed that this enzyme is active, thermo-stable and maintains its quaternary arrangement even after substantial (ca 33 %) cleavage of the protein. The results presented in this manuscript thus show that the DSBH scaffold offers a novel balance between protein stability and function by locating the active site and substrate recognition features in the most stable region of the protein.
Keywords: Double stranded beta helix, Cupin, Quercetinase, Conformational stability, Fragment complementation, Oligomerization