Abstract
Cellular functionalities are contingent upon the ability of proteins to maintain or transform their shape (conformation). The molecular forces that govern protein folding have long been known. These include hydrophobic interactions, hydrogen bonding, and disulfide bonds. However, how proteins maintain their conformation remains largely unanswered. In this study, twenty G proteins from Saccharomyces cerevisiae were cloned, purified from E. coli, and tested for conformational stability. The proteins vary in Tm from 35 to 60°C. This is paradoxical considering their highly analogous crystal structures and identical catalytic activity. We find that thermal stability correlates with percentage of Cys, Met, or Pro residues in the primary sequence. We also find that the stabilities group by their respective family members, with the following trend observed for least to most thermostable G proteins: Rho/Cdc42 < Ran < Large G‐proteins < Ras < Rab < Sar/Arf. Both these results suggest that thermal stability has a greater dependence on primary sequence than tertiary structure. Ultimately, a more detailed understanding of protein stability can help in engineering enzymes for new molecular therapeutics.
Grant Funding Source: Supported by National Science Foundation REU Site Award 1156840 to UNC‐Chapel Hill