Figure 4.

NS3h‐mediated ssDNA shortening. A: Schematic representation of NS3h‐mediated ssDNA shortening. Long ssDNA was stretched with the optical trap at constant force. To keep the force constant, feedback control allowed to adjust the distance between trap center and the 5′‐end of ssDNA automatically. Stage position recording allowed the observation of the shortening effect. B: Force trajectory and time‐lapse recording of ssDNA length. The ssDNA tether length gradually decreases and suddenly increases in a periodic pattern. The detected force keeps in a constant while tether length of ssDNA gradually decreases, and force relaxation occurs when the total tether length of ssDNA increases. The shortening of ssDNA length is mediated by NS3h. The increase in tether length shown by force relaxation indicates that NS3h either fully or partially dissociates from the ssDNA. C: Processivity of NS3h‐mediated ssDNA shortening. The shortened distance mediated by NS3h was determined by fitting first order decay function (light gray curve), the inverse of the decay constant is 150 ± 6 nt. D: Shortening rate measured as a function of applied force to ssDNA. Mean shortening rate and s.e.m. are listed: 39.1 ± 1.9 nt/s, 32.7 ± 2.5 nt/s, 24.6 ± 0.6 nt/s, 23.7 ± 1.1 nt/s. Force‐dependent behavior can be seen.