CRC 858 B13 - Molecular basis for the cooperative action of a helicase and a topoisomerase domain in reverse gyrase in positive DNA supercolling (SFB 858)

Basic data for this project

Description

The combined action of helicases and topoisomerases is central to maintaining genome stability in many organisms, including humans, and defects lead to severe diseases and death. While helicases use the energy of ATP hydrolysis, DNA topoisomerases inter-convert different topological states of DNA. Reverse gyrase is a unique enzyme that is capable of introducing positive supercoils into DNA at the expense of ATP hydrolysis. This novel function is achieved by the functional cooperation of a helicase-like and a topoisomerase domain. The helicase-like domain binds and hydrolyzes ATP, and cooperates with the topoisomerase domain that catalyzes DNA cleavage, and strand passage towards positive supercoiling. Reverse gyrase serves as a model system for understanding the functional cooperation of helicases and topoisomerases in general. We have already shown that the isolated helicase-like domain of reverse gyrase binds ATP and DNA cooperatively, and provides a nucleotide-dependent DNA binding site for reverse gyrase. Reverse gyrase is more than the sum of its parts: In this project, we will dissect the molecular basis for the functional cooperation of the helicase and topoisomerase modules in reverse gyrase that lead to the generation of the novel function of ATP-dependent positive DNA supercoiling. Overall, the results will provide a comprehensive understanding at the molecular level of the functional cooperation of the two domains in reverse gyrase, and provide insight into the functional cooperation of helicase and topoisomerase domains in general.