Proc. Natl Acad. Sci. USA doi:10.1073/pnas.0907404106 (2009)

DNA polymerase enzymes that are responsible for DNA replication can work faster than previously thought.

Using a type of fluorescence spectroscopy, Jerrod Schwartz and Stephen Quake at Stanford University in California studied single polymerase molecules from the bacterium Escherichia coli in real time.

The enzyme pauses periodically as it travels along a strand of DNA synthesizing a partner strand, and the researchers measured its speed during periods of movement. They showed that the DNA polymerase Pol I(KF) has an intrinsic speed limit of 14–17 nucleotides per second, depending on the conditions — about ten times greater than estimates based on averages of all of its movements, including pauses. Another polymerase they looked at had a highly variable synthesis rate, ranging from 1 to about 50 nucleotides per second.