Polyhistidine length impacts purification of spike-His-Fer,
but
not HA-His-Fer. (A) Site 4, as in Figure 1, highlighting the length of the installed
polyhistidine tag, ranging from four to eight histidine residues.
The image in panel A shows installation of six histidine residues.
Dot blots tracking the purification of His-4.4–His-4.8 proteins
for either (B) HA or (C) spike. Columns show dots from the load, flow
through (FT), wash (W), or elution (Elu). Expression was detected
for all lengths of HA-His-Fer but only for greater than or equal to
six histidine residues for spike-His-Fer. (D) SDS–PAGE analysis
of the elution from the dot blots shown in panels B and C. Lanes in
HA-His-Fer correspond to a molecular weight (MW), in kilodaltons,
ladder (lane 1, labels on the left), His-4.4–His-4.8 (lanes
2–6, respectively), and the WT (lane 7). Lanes in spike-His-Fer
correspond to the MW ladder (lane 1, labels on the left), the WT (lane
2), and His-4.4–His-4.8 (lanes 3–7, respectively). These
results confirm the dot blot analysis and demonstrate that the proteins
migrate at the expected MW.