An Intriguing Investigation into the Effects of Carboxyl-Terminal Truncations on Protein Solubility
By: Dominic Guidry, Hazel Leiva
Department: Chemistry & Biochemistry
Faculty Advisor: Dr. Misty Kuhn
Histone acetyltransferase MCC1 isoform X1 belongs to the Gcn5-related N-acetyltransferase (GNAT) superfamily of proteins that acylate substrates using different acyl-CoA donors. This protein is a homolog of some of the hypothetical polyamine acetyltransferase enzymes we have been studying in our laboratory. Some of these proteins have proven difficult to express and, or, to solubilize for downstream protein purification. One hypothesized culprit for this difficulty is a predicted C-terminal alpha helical extension that directs the proteins to organelles or membranes. Previous research has shown that truncation of the C-terminus of the MCC1 protein avoids protein aggregation and improves solubility. We hypothesized that a truncated version of our homologous proteins will also improve soluble protein production. However, we were unsure how much of the C-terminus should be removed and whether some truncations would disrupt key amino acid interactions within the protein and make the protein misfold. Therefore, we created a series of four truncated versions of a predicted polyamine acetyltransferase protein, which was insoluble in previous experiments. For the purpose of this presentation, we focus on two truncations, the deletion of 70 amino acids (delta 70) for one variation, and 68 amino acids (delta 68) for the other. Here, we compare our findings for these constructs for soluble protein expression and purification and models of the truncated proteins. While more experimentation is needed, our results show these truncations are providing progress toward soluble protein production.