Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Long-Sought Protein Structure May Show How ‘Gene Switch’ Works

10.02.2009
The bacterium behind one of mankind’s deadliest scourges, tuberculosis, is helping researchers at the Commerce Department’s National Institute of Standards and Technology (NIST) and the Department of Energy’s Brookhaven National Laboratory (BNL) move closer to answering the decades-old question of what controls the switching on and off of genes that carry out all of life’s functions.

In a Journal of Biological Chemistry paper* posted online this week, the NIST/BNL team reports that it has defined—for the first time—the structure of a “metabolic switch” found inside most types of bacteria—the cyclic AMP (cAMP) receptor protein, or CRP—in its “off” state.

CRP is the “binding site” (attachment point) for cAMP, a small molecule that, once attached, serves as the signal to throw the switch. This “on” state of CRP then turns on the genes that help a microbe survive in a human host.

The researchers hope that once the switching mechanism is understood the data can be used to develop new methods for preventing tuberculosis and other pathogenic bacterial diseases.

“We know that many pathogenic bacteria use cAMP as a signal for activating genes that keep the microbes thriving in adverse conditions, and therefore, remaining virulent,” says NIST biochemist and lead author Travis Gallagher. “Blocking these processes might provide ways to shut down infections and save lives.”

Additionally, the researchers believe that learning how this specific protein switch works may provide insight into how genes in general are regulated.

The biochemical puzzle surrounding the CRP switch is the mechanism by which the protein binds cAMP at one end, then attaches to—and activates—a gene (DNA) at the other end. Believing that the protein somehow changes its overall shape after binding cAMP, researchers set out 25 years ago to study the structure of CRP in both its active state (with cAMP bound to it) and inactive state (without bound cAMP) to document where the morphing occurs.

Unfortunately, the task proved to be extremely difficult. Using CRP from the bacterium Escherichia coli, researchers were able to crystallize the protein in its active (“on”) state and examine the structure using a technique called X-ray diffraction. However, the structure of the inactive (“off”) E. coli CRP eluded them as attempts to crystallize it repeatedly failed. With only the structure of the “on” state defined, the genetic switching mechanism remained a mystery.

The breakthrough was achieved when Gallagher; NIST colleagues Prasad Reddy, Natasha Smith and Sook-Kyung Kim; and BNL’s Howard Robinson substituted the CRP from Mycobacterium tuberculosis [the pathogen that causes tuberculosis] for the E. coli protein.

The team’s initial success—obtaining crystals of CRP in the “off” state—was dramatic given that no one had accomplished the feat in nearly three decades of trying with E. coli. But the real excitement came when the crystals were examined with X-ray diffraction.

“Although the M. tuberculosis protein in the ‘off’ state consists of two subunits that are genetically identical, we were surprised to see that the subunits were not structurally symmetrical as well,” Gallagher says. “In most two-subunit proteins, each subunit has the same conformation as the other.”

Gallagher says that the NIST/BNL team theorizes that it is the asymmetry in the absence of cAMP that prevents the protein from attaching to DNA. This, in turn, keeps CRP from activating genes when they are not needed.

“Our next step is to crystallize M. tuberculosis CRP in the active state and define its structure,” Gallagher says. “When that is accomplished, we’ll be able to see the identical protein from the same organism in both states, which may give us the means to explain how CRP switches from its asymmetric form [inactive state] to its symmetrical [active state] form.”

The work detailed in the Journal of Biological Chemistry paper was performed at the University of Maryland Biotechnology Institute (UMBI)’s Center for Advanced Research in Biotechnology (CARB), a partnership among UMBI, NIST and Montgomery County, Md., that advances biotechnology by integrating chemical, physical and biomolecular sciences through research on biomolecular structure and function, systems biology and biometrology, and through the development of new technologies for measurement, analysis and design.

As a non-regulatory agency, NIST promotes U.S. innovation and industrial competitiveness by advancing measurement science, standards and technology in ways that enhance economic security and improve our quality of life.

* D.T. Gallagher, N. Smith, S-K Kim, H. Robinson and P.T. Reddy. Profound asymmetry in the structure of the cAMP-free cAMP receptor protein (CRP) from Mycobacterium tuberculosis. Journal of Biological Chemistry (published online Feb 4, 2009).

High-resolution versions of the graphics showing the "on" and "off" states of the TB cAMP receptor protein are available http://www.nist.gov/public_affairs/releases/tuberculosis.html.

A short video featuring NIST biochemist Travis Gallagher explaining how the TB cAMP receptor protein "gene switch" works is available at http://www.youtube.com/watch?v=3hpuu3maOhk.

Michael E. Newman | Newswise Science News
Further information:
http://www.nist.gov

More articles from Life Sciences:

nachricht Newly designed molecule binds nitrogen
23.02.2018 | Julius-Maximilians-Universität Würzburg

nachricht Atomic Design by Water
23.02.2018 | Max-Planck-Institut für Eisenforschung GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Good vibrations feel the force

A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.

By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

A Keen Sense for Molecules

23.02.2018 | Physics and Astronomy

“Laser Technology Live” at the AKL’18 International Laser Technology Congress in Aachen

23.02.2018 | Trade Fair News

Newly designed molecule binds nitrogen

23.02.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>