Function of a viral genome packaging motor from bacteriophage T4 is insensitive to DNA sequence

Many viruses employ motors to translocate DNA into capsids. Previous reports raise questions if motor function depends on DNA sequence and a “B-A scrunchworm” model predicts that “A-philic” sequences that transition more easily to A-form would alter function. We use optical tweezers to measure translocation of phage, plasmid, and synthetic A-philic, GC rich sequences by the T4 motor. We observed no differences in motor velocities, even with A-philic sequences predicted to show higher rate, no changes in motor pausing, and only modest changes in slipping. To test more generally for sequence dependence, we conducted correlation analyses across pairs of events. No significant correlations in packaging rate, pausing, or slipping versus position were detected in repeated measurements with different DNA sequences. These studies suggest that the viral motor insensitive to DNA sequence and fluctuations in packaging velocity, pausing, and slipping are primarily stochastic temporal events.