How RNA polymerase moves

The molecule appears to shift along nucleic acid using a ratchet system, researchers report

Charles Choi(
Jan 27, 2005

Investigators may have uncovered the general mechanism that governs RNA polymerase movement, they report in the January 28 issue of Cell.

The finding "provides a framework for understanding how numerous external regulatory signals converge to change the properties of the RNA polymerase active site," co-author Evgeny Nudler of New York University told The Scientist.

Nudler and colleagues explored RNA polymerase's F bridge helix at its elongation complex's catalytic center. In 2001, Roger Kornberg at Stanford University and colleagues suggested the F bridge drives the enzyme forward by switching between its bent and straight conformations.

Using a genetic screen, the researchers isolated two mutations in Escherichia coli RNA polymerase's G loop, a region adjacent to the F bridge that recent studies suggested regulated F bridge conformation. One, G1136S, led to faster elongation as well as rendering RNA polymerase poorly responsive to pauses and terminators. The other, I1134V, rendered...

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