Navigation Links
University of Pittsburgh researchers crack code of 3-D structure in key metabolic protein
Date:3/10/2008

PITTSBURGH, March 10 Using X-ray crystallography, researchers at the University of Pittsburgh School of Medicine led by structural biologist Joanne I. Yeh, Ph.D., have become the first to decipher the three-dimensional structure of a membrane-bound enzyme that plays a crucial role in glycerol metabolism a discovery that could lead to important advances against obesity, diabetes and a potential host of other diseases. Their findings are reported in the March 4 issue of the Proceedings of the National Academy of Sciences.

The sugar-alcohol glycerol is an essential source of energy that is required to help drive cellular respiration. In addition to powering some of the most central reactions of the body, glycerol also provides key precursors needed to regulate fatty acid and sugar metabolism. Figuring out the complex ways that cells break down or produce glycerol and use this vital chemical could be critical to combating obesity, diabetes and other chronic disorders. Recent findings also have linked glycerol metabolism to cellular processes related to aging, infectivity in certain organisms such as Mycobacterium tuberculosis, and in other energy-related illnesses.

Everybody wants a golden bullet for obesity, and certainly we need better ways of controlling diabetes, said Dr. Yeh, the studys senior author and associate professor of structural biology at Pitt. I think that glycerol metabolism will be on the forefront of developing treatments for these diseases, and so many others, since it is a pivotal yet underappreciated link among some very important metabolic pathways.

The protein structure Dr. Yehs team solved is a large enzyme called Sn-glycerol-3-phosphate dehydrogenase known simply as GlpD found in abundance in the cell membranes of almost all organisms, including humans. GlpD is a monotopic membrane protein, which means that although it is embedded partially into the cell membrane, the protein does not span the entire membrane to the interior of the cell. As a result, it is technically challenging to produce enough highly purified and active protein to obtain clear, relevant information about the enzymes atomic structure. This study marks the highest resolution structure of a monotopic membrane protein that scientists have solved to date, and is one of only a handful of structures of this important class of membrane proteins that have been determined.

These findings and data help to fill an important scientific and technical gap in the structural field and present new information and ideas about how the enzyme works and the importance of the cell membrane in stabilizing the enzyme and in processes related to energy production, said Dr. Yeh, who published the paper along with postdoctoral research associate Unmesh N. Chinte, Ph.D., and research assistant professor, Shoucheng Du, Ph.D., both in Pitts Department of Structural Biology.

Studying the proteins and enzymes involved in oxidative and glycerol metabolism, as well as characterizing their structures, functions and regulatory relationships, has been a major research interest of Dr. Yehs lab. It took Dr. Yeh and her colleagues only three months an unusually short time to decipher the set of 3-D structures of GlpD isolated from E. coli bacteria, thanks to other methodologies they developed in earlier studies.

Rather than make conclusions based on a single structure, the team additionally determined the structures of GlpD bound with its metabolic product and several substrate analogues to evaluate the enzyme in its native and combined forms. By careful unraveling of this collection of structures, researchers could gain a more complete understanding of how the enzyme functions, details about how GlpD interacts with the membrane, works to catalyze the enzymatic reaction, and links to cellular-energy production.

As part of these challenging studies, the Pitt researchers used novel peptide-based detergents called peptergents that they developed in their lab to carefully separate GlpD from the cell membrane and keep it in an active form to ensure that their studies revealed a physiologically relevant enzyme structure. The team then used detergents to crystallize the enzyme and screened the protein crystals in Pitts new state-of-the-art X-ray crystallography facility, directed by Dr. Yeh.

Next, they applied beams of high intensity parallel X-rays to the protein crystals in order to collect the diffraction data necessary to determine the proteins atomic configuration. These experiments were performed using cyclic particle accelerators at the Argonne National Laboratory in Illinois and the Paul Scherrer Institute in Switzerland. Called synchrotrons, these accelerators are the size of a football field and produce X-ray beams millions of times more intense than those generated by conventional X-ray machines. Highly advanced computational techniques were then used to analyze the diffraction data and to uncover, through complex mathematical approaches, the atomic matter in the crystals responsible for the diffraction. Ultimately, the unique 3-D topology of GlpD was deciphered, atom by atom.

The main role of GlpD in the cell is to remove hydrogen from a form of glycerol called glycerol-3-phosphate (G3P) to generate dihydroxyacetone phosphate (DHAP), a biochemical compound vital to the process of metabolizing the sugar-alcohol. In the process, electrons are produced and shuttled to a molecule called ubiquinone that works to power cellular respiration. Based on the structural information acquired in their study, Dr. Yehs team proposed mechanisms by which the enzyme carries out this fundamental metabolic reaction.

Their data revealed that GlpD is a dimer, or a protein with two subunits, that is embedded into and interacts substantially with the lipids that make up the cell membrane. This interaction with the membrane is required to keep the enzyme energetically and functionally stable so that it doesnt collapse on itself, the PNAS study reports.

Dr. Yehs team also found that the enzyme is made up of two major domains: a soluble extracellular cap and a FAD-binding region, whose base is rooted in the membrane. The location of the enzymes active site where the chemical reaction actually occurs is at this FAD-binding region. G3P fastens tightly here, much like a key fitting into a lock, and is then transformed into DHAP. The researchers also proposed a docking site for where ubiquinone binds to the enzyme to accept electrons produced in the reaction. Eventually, ubiquinone feeds these electrons into respiration to produce the crucial energy to fuel cellular processes.

In addition, Dr. Yehs team discovered a never-before-seen type of protein fold consisting of about 100 amino acids in the cap domain of GlpD. They also identified areas where other proteins might bind to regulate the enzymes activity and transmit chemical signals.

With the GlpD structure in hand, Dr. Yehs team is already examining how mutating, or changing, certain amino acids in the enzyme affects its function and fold. These studies target the roles that these specific amino acids play in enzymatic function and regulation of activity. These questions are important because glycerol metabolism is a key link between sugar and fatty acid metabolism. The Pitt group also has determined the atomic resolution structures of other enzymes involved in mediating glycerol and oxidative metabolism. In all, these structural results provide some of the first three-dimensional views of these highly important proteins and enzymes.


'/>"/>

Contact: Michele Baum
BaumMD@upmc.edu
412-647-3555
University of Pittsburgh Schools of the Health Sciences
Source:Eurekalert

Related medicine news :

1. Case Western Reserve University researchers identify colorectal cancer gene
2. New research from the University of Bristol aims to eliminate Streptococcus infections
3. Iowa State University researcher identifies eye disease in canines
4. Robert H. Smith Feeding the Future with $15 Million Gift to Hebrew University of Jerusalem
5. AT&T Provides In-Building Wireless Services to Thomas Jefferson University and Hospital
6. St. Louis University Hospital Purchases Second CyberKnife(R) System
7. Loma Linda University Medical Center Celebrates Groundbreaking on Inland Empires Most Comprehensive Rehabilitation Center
8. Alimera Sciences Signs Second Agreement With Emory University for Potential Treatments Using New Class of Antioxidants
9. University of Sydney researchers find new evidence linking kava to liver damage
10. University of Denver bullying victimization study
11. The Northern Illinois University Murders Due to Chemical Imbalances or Chemical Balancers - Drugs? - Fred A. Baughman Jr., MD, Neurologist/Child Neurologist
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:2/24/2017)... ... ... two months after the official release of The Private Collection – Edition 2017 at ... a second print-run of its lavish luxury travel coffee table book. , An ... at more than six kilos, retails at EUR 1,000 per copy and is packed ...
(Date:2/24/2017)... ... 24, 2017 , ... An in-depth computational analysis of genetic variants implicated in ... eight genes that may explain why susceptibility to one of the disorders could place ... published today in the journal npj Schizophrenia. , “There is a wealth of ...
(Date:2/24/2017)... ... February 24, 2017 , ... The Smart Machine Age is here, ... predict that 47 percent of all jobs in the United States may be taken ... The day of the aggressive know-it-all who steamrolls over colleagues is drawing to a ...
(Date:2/24/2017)... (PRWEB) , ... February 24, 2017 , ... ... and hearing disabilities, it is so critically important that we all are aware ... That is why Mediaplanet is proud to announce the launch of its newest ...
(Date:2/24/2017)... ... , ... The narrative in “ Signal 8: An Australian Paramedic’s Story ” ... paramedic experiences. Schanssema describes the tragedies he saw, as well as his struggles with ... Schanssema, initially unsure of the career path he wanted to take, found fulfillment in ...
Breaking Medicine News(10 mins):
(Date:2/24/2017)... Research and Markets has announced the addition of the "Global ... report to their offering. ... The Global Empty Capsules Market is poised to grow at a CAGR ... by 2025. This industry report analyzes the market estimates ... regional levels presented in the research scope. The study provides historical market ...
(Date:2/24/2017)... , Feb. 24, 2017 Medical information ... to increase their self-service capabilities to manage inquiries ... (HCPs). New research from consulting leader ... have developed self-service website portals where HCPs can ... just one of many findings to emerge from ...
(Date:2/24/2017)... ITL Limited, ( ASX : ITD ), une société de ... excellents résultats semestriels clos le 31 décembre 2016 par ... « Résultats et mise à jour sur la croissance biomédicale ... Faits marquants Bénéfice ... hausse de 104 %) Bénéfice par action ...
Breaking Medicine Technology: