Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Study details structural changes of a key catalytic enzyme

25.09.2006
Findings challenge traditional hypothesis, may aid in drug design

Enzymes are complex proteins capable of catalyzing specific biochemical reactions in cells. While it has long been recognized that dynamic fluctuations in protein conformation or structure play a central role in enzyme catalysis, the new findings indicate that the "dynamic energy landscape" of the enzyme funnels it along a preferred pathway that actually minimizes the number and dimension of the energetic barriers to these catalytic changes.

"There is a growing awareness that the inherent motions of proteins are essential to their functions," said Peter Wright, who is chair of the Scripps Research Department of Molecular Biology and a member of the Skaggs Institute for Chemical Biology at Scripps Research. "The importance of this study is that it reveals how dynamic structural fluctuations channel an enzyme through its reaction cycle-the thermal motions of the protein are harnessed to perform its biological function, in this case, catalysis. Knowledge of the excited-state conformations of proteins may offer new opportunities for drug design."

The researchers used nuclear magnetic resonance (NMR) to detect and characterize higher energy structural sub-states (excited states) of E. coli dihydrofolate reductase, which has been used extensively as a model enzyme for investigating the relations between structure, dynamics, and function in proteins. The researchers found that, at each stage in the catalytic cycle, the excited-state conformations resembled the ground-state structures of both the preceding and the following intermediates. This means that the dynamic fluctuations between the ground state and the excited state were "priming" the enzyme to take up the conformation of the adjacent intermediate state, facilitating the progress of catalysis by aiding the movement of ligands (molecules that bind to one chemical entity to form a larger complex) on and off the enzyme.

"These findings contrast with the traditional 'induced fit' hypothesis," Wright said. "One of the tenets of that hypothesis is that the binding of ligands induces a structural change that increases the complementary relationship between the ligand and the enzyme."

As the study points out, most proteins do not have rigid molecular structures but are structurally heterogeneous; the motion and plasticity in their structure allows them to achieve a far greater range of functions than would be possible with static structures.

However, despite considerable evidence that many enzymes are inherently flexible, the fundamental mechanisms by which protein fluctuations couple with catalytic function remain poorly understood.

In the new conformational model, a small number of minor conformational sub-states that resemble the ligand-bound conformations are already present in solution. When the ligand binds to the minor sub-state, it causes an equilibrium shift so that the ligand-bound conformation becomes the new major sub-state.

"Our study can be placed in the broader context of the catalytic cycle," Wright said. "The results imply that for each of the intermediates in the catalytic cycle of DHFR, the lowest energy excited states are the most functionally relevant conformations. The enzyme structure responds to ligands by taking up a preferred ground-state conformation, but also samples other relevant conformations of higher energy, enabling it to rapidly advance to the next steps in catalysis. As ligands change, the energy landscape and the accessible states of the enzyme change in response. Consequently, this dynamic energy landscape efficiently funnels the enzyme along a specific kinetic path, where the number and heights of the barriers between consecutive conformations have been minimized."

Keith McKeown | EurekAlert!
Further information:
http://www.scripps.edu

Further reports about: Catalysis Dynamic Ligand catalytic enzyme fluctuations sub-state

More articles from Life Sciences:

nachricht How brains surrender to sleep
23.06.2017 | IMP - Forschungsinstitut für Molekulare Pathologie GmbH

nachricht A new technique isolates neuronal activity during memory consolidation
22.06.2017 | Spanish National Research Council (CSIC)

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>