The SARS Coronavirus E Protein Interacts with PALS1 and Alters Tight Junction Formation and Epithelial Morphogenesis

Teoh, Kim-Tat; Siu, Yu-Lam; Chan, Wing-Lim; Schlüter, Marc A.; Liu, Chia-Jen; Peiris, J. S. Malik; Bruzzone, Roberto; Margolis, Benjamin; Nal, Béatrice

To verify this hypothesis, we prepared a mutant in which these four amino acids were deleted and performed GST-pull down assays in which GST-PALS1 fusion proteins were incubated with cell lysates containing either E wild type or a truncation mutant of E, named E (wt) and E (ΔPBM), respectively. Strikingly, both GST-PALS1 fusion proteins (clone 131 and PDZ) efficiently pulled down HA-E (wt), but not HA-E (ΔPBM) (Figure 4A, panels a and b, lanes 3–6). Of note, the HA tag on SARS-E did not affect the strength of the interaction with GST-PALS1 fusion proteins (data not shown). We also did not observe any nonspecific binding with beads, GST protein (data not shown), and GST-PALS1 (SH3) fusion protein (Figure 4A, panels a and b, lanes 7–8), which were included as negative controls. These results indicate that the D-L-L-V motif, which is located at the carboxy-terminal extremity of E protein, is a PDZ domain-binding motif that enables interaction with PALS1 PDZ domain in vitro.