A walk down the strand

摘要

Many transactions involving DNA generate a single-stranded intermediate that is protected from degradation by ssDNA-binding (SSB) protein. Whilst protecting the DNA, this protein needs to allow rapid access to other proteins, such as polymerases or repair factors, for subsequent DNA processing. A mechanism that allows SSB to stay firmly bound to the ssDNA whilst allowing access has been found in a single-molecule fluorescence resonance energy transfer study of the E. coli protein. This SSB is a tetramer that wraps ssDNA around its exterior. Surprisingly, it can migrate via a random walk along the ssDNA, so it can be repositioned although it remains tightly bound.