The life cycle of a protein observed by a single molecule solution

Using a highly sensitive technique, a single-molecule measurement technique, scientists at the University of Illinois at Urbana-Champaign observed the life cycle of RecA, a protein that plays a big role in the repair process. AND molecules are destroyed.

Scientists at the University of Illinois observed the life cycle of RecA, a protein that plays a major role in the repair of destroyed DNA molecules.A clearer understanding of how proteins work can help us better understand cancer.(Photo: Taekjip Ha (left) , professor of physics, and one of his co-authors, graduate student Chirlmin Joo (taken by L. Brian Stauffer))

Proteins are small, developed and shrunk into monomers at one time.

RecA is a DNA recombinant protein found in the intestine of E. coli bacteria. A type of homolog, called Rad51, interacts with many other proteins, including BRCA2, when their levels increase dramatically, leading to breast and ovarian cancer. A clearer understanding of how proteins work can help us better understand cancer.

' Our measurement technique provides a way to count the number of independent monomers surrounding a DNA molecule for a certain period of time, ' said Taekjip Ha, a professor of physics at Illinois and an investigator of Learning. Howard Hughes Medical Institute, said: ' With this technique, we can show the kinetic rate of reactions occurring at the same time as the protein formation of proteins '.

During the recombination process, RecA forms a microfiber twist around DNA molecules. This microfiber can grow in many directions, and can grow on DNA molecules by growing at one end and splitting at the other end.

To study RecA's dynamic process, the researchers used very sensitive analytical techniques, single-molecule fluorescence resonance energy (FRET) techniques by Professor Ha and his colleagues. I develop.

To use the FRET technique, scientists first attach two dye molecules - one blue and one red - to the molecule they want to study. After that, they stimulated the blue dye with a laser. Some of the energy is transferred from the blue dye to the red substance, depending on the distance between them.

The scientists then measured the brightness of the two dyes at the same time. The change in the ratio between the two intensities indicates the relative displacement of the two dyes, and hence the molecular motion or its size change.

This technique has allowed solving complex problems about how RecA nuclei form microfiber forms, how they change shape, and how they separate protein molecules from ADN.

' Contrary to the initial expectations, both ends of RecA yarns grew and shrunk, but a faster twisting speed at one end caused the main yarn to grow in one direction ', Ha said. know. ' We also know that when this fiber grows and shortens, it behaves like a unit protein at that time .'

Further examination of each step of the process of recombining proteins can help scientists show how cancer-causing protein molecules become defective, and thus can find ways to repair them.

Along with Ha, co-authors include graduate students Chirlmin Joo and Sean A. McKinney, graduate student Muneaki Nakamura, and scientists Ivan Rasnik and Sua Myong. The work belongs to the research program of the National Science Foundation and the National Institutes of Health.

Le Pham Thanh (Translated by ScienceDail, August 12, 2006)