Extended Data Figure 7: Generation of entropic force at the end of an unfolded polypeptide chain anchored to, and confined in, a narrow channel (in support of Supplementary Information section 3).
a, Depiction of the transit of an unfolded polypeptide chain (blue) anchored through its N terminus at the tip of a narrow channel (with a diameter of d and length of R). The pulling force (F, red arrow) at the C terminus of the polypeptide chain is generated by the total number (N) of free unfolded residues of length (a). b, Depiction of the increase in pulling force F(R,Na) as residues of the polypeptide chain crystallize at the tip of the channel, reducing the number of free residues within the channel, resulting in an increase in the ratio (R/Na) between channel length and number of free unfolded residues. This leads to an overstretched regime where the pulling force rapidly increases to reach the critical force (FM; dashed line) required to capture the awaiting subunit docked at the export machinery.
