Mutations altering a structurally conserved loop-helix-loop region of a viral packaging motor change DNA translocation velocity and processivity.

ABSTRACT: Many double-stranded DNA viruses employ ATP-driven motors to translocate their genomes into small, preformed viral capsids against large forces resisting confinement. Here, we show via direct single-molecule measurements that a mutation T194M downstream of the Walker B motif in the phage lambda gpA packaging motor causes an 8-fold reduction in translocation velocity without substantially changing processivity or force dependence, whereas the mutation G212S in the putative C (coupling) motif causes a 3-fold reduction in velocity and a 6-fold reduction in processivity. Meanwhile a T194M pseudorevertant (T194V) showed a near restoration of the wild-type dynamics. Structural comparisons and modeling show that these mutations are in a loop-helix-loop region that positions the key residues of th

SUBMITTER: Tsay JM 

PROVIDER: S-EPMC2911301 | biostudies-literature | 2010 Jul

REPOSITORIES: biostudies-literature