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. Author manuscript; available in PMC: 2018 May 3.
Published in final edited form as: Adv Exp Med Biol. 2012;726:549–584. doi: 10.1007/978-1-4614-0980-9_24

Figure 6.

Figure 6

High-resolution measurement of φ29 step size. A) Burst-dwell behavior. At low tensions (~8 pN) packaging was observed to occur in large 10-bp “bursts” separated by flat “dwells”. The behavior was seen across the full range of ATP, from 10 μM (black data) to 500 μM (purple). B) Dwell time distributions. The duration of each dwell in the stepping traces was measured and used to compile a probability distribution at each ATP concentration (same color code as A). The distributions were peaked rather than exponential, indicating that multiple rate-limiting kinetic steps occurred during the dwells. C). Sub-step size. At higher tensions (~40 pN) and at 250 μM ATP, conditions under which DNA translocation is rate-limiting, the 10-bp bursts were observed to consist of four 2.5-bp substeps. D) Model of intersubunit coordination in φ29. Packaging occurs via a biphasic mechanism in which the gp16 ring loads multiple (most likely 4) ATPs during “dwells”, and translocates the DNA in 4 rapid and successive 2.5-bp sub-steps during the 10-bp “bursts”.