Fig. 2.

Comparison of signal peptides on the expression of H6HA1-His.

Three signal peptides were added respectively to the upstream of the H6HA1-His sequence to enhance the secretion of the H6HA1-His protein. These peptides (hAZsp, AIVsp, and GP67sp) and their amino acid sequences are presented in Supplementary Table S1. (A) The expressed proteins in the medium of the cell cultures were collected by ammonium sulfate precipitation (AS), and then nickel affinity chromatography was applied. After the unbound proteins (Ub) were washed out, the H6HA1-His proteins were eluted from the column using imidazole gradients that were detected in Western blotting using an anti-HA antibody. All experiments were performed under the same conditions for comparison. (B) The expressed H6HA1-His proteins from the cell pellet (Cell) or the supernatant (Sup) were compared using Western blotting, for which their protein amount was adjusted to be equal. No signal peptide was added in the control experiments.