<p>One or two leucine residues of a class 1a NES at the Φ1, Φ3, or Φ4 conserved hydrophobic positions, indicated on the top line, were replaced with cysteine, phenylalanine, threonine or tryptophan, as highlighted in blue, and the nuclear export activity was assayed in NIH3T3 cells. The indicated activity scores were determined as in <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003841#pcbi.1003841.s001" target="_blank">Figure S1</a>. Note that the effects of the substituted residues on the NES activity scores were roughly independent and additive.</p
