Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Antibacterial protein’s molecular workings revealed

22.02.2013
On the front lines of our defenses against bacteria is the protein calprotectin, which “starves” invading pathogens of metal nutrients.
Vanderbilt investigators now report new insights to the workings of calprotectin — including a detailed structural view of how it binds the metal manganese. Their findings, published online before print in the Proceedings of the National Academy of Sciences, could guide efforts to develop novel antibacterials that limit a microbe’s access to metals.

The increasing resistance of bacteria to existing antibiotics poses a severe threat to public health, and new therapeutic strategies to fight these pathogens are needed.
The idea of “starving” bacteria of metal nutrients is appealing, said Eric Skaar, Ph.D., MPH, associate professor of Pathology, Microbiology and Immunology.

In a series of previous studies, Skaar, Walter Chazin, Ph.D., and Richard Caprioli, Ph.D., demonstrated that calprotectin is highly expressed by host immune cells at sites of infection. They showed that calprotectin inhibits bacterial growth by “mopping up” the manganese and zinc that bacteria need for replication.

Now, the researchers have identified the structural features of calprotectin’s two metal binding sites and demonstrated that manganese binding is key to its antibacterial action.

Calprotectin is a member of the family of S100 calcium-binding proteins, which Chazin, professor of Biochemistry and Chemistry, has studied for many years. Chazin and postdoctoral fellow Steven Damo, Ph.D., used existing structural data from other S100 family members to zero in on calprotectin’s two metal binding sites. Then, they selectively mutated one site or the other.

They discovered that calprotectin with mutations in one of the two sites still bound both zinc and manganese, but calprotectin with mutations in the other site only bound zinc.

The researchers recognized that these modified calprotectins — especially the one that could no longer bind manganese — would be useful tools for determining the importance of manganese binding to calprotectin’s functions, Chazin noted.

Thomas Kehl-Fie, Ph.D., a postdoctoral fellow in Skaar’s group, used these altered calprotectins to demonstrate that the protein’s ability to bind manganese is required for full inhibition of Staphylococcus aureus growth. The investigators also showed that Staph bacteria require manganese for a certain process the bacteria use to protect themselves from reactive oxygen species.

“These altered calprotectin proteins were key to being able to tease apart the importance of the individual metals — zinc and manganese – to the bacterium as a whole and to metal-dependent processes within the bacteria,” Skaar said. “They’re really powerful tools.”

Skaar explained that calprotectin likely binds two different metals to increase the range of bacteria that it inhibits. The investigators tested the modified calprotectins against a panel of medically important bacterial pathogens.

“Bacteria have different metal needs,” Skaar said. “Some bacteria are more sensitive to the zinc-binding properties of calprotectin, and others are more sensitive to the manganese-binding properties.”

To fully understand how calprotectin binds manganese, Damo and Chazin — with assistance from Günter Fritz, Ph.D., at the University of Freiburg in Germany — produced calprotectin crystals with manganese bound and determined the protein structure. They found that manganese slips into a position where it interacts with six histidine amino acids of calprotectin.

It’s really beautiful; no one’s ever seen a protein chelate (bind) manganese like this,” Chazin said.“It’s really beautiful; no one’s ever seen a protein chelate (bind) manganese like this,” Chazin said.

The structure explains why calprotectin is the only S100 family member that binds manganese and has the strongest antimicrobial action, and it may allow researchers to design a calprotectin that only binds manganese (not zinc). Such a tool would be useful for studying why bacteria require manganese — and then targeting those microbial processes in new therapeutic strategies, Chazin and Skaar noted.

“We do not know all of the processes within Staph that require manganese; we just know if they don’t have it, they die,” Skaar said. “If we can discover the proteins in Staph that require manganese — the things that are required for growth — then we can target those proteins.”

The team recently was awarded a five-year, $2 million grant from the National Institute of Allergy and Infectious Diseases (AI101171) to advance their studies of calprotectin and how it works to limit bacterial infections and in other inflammatory conditions.

“Nature stumbled onto an interesting antimicrobial strategy,” Chazin said. “Our goal is to really tease apart the importance of metal binding to all of calprotectin’s different roles — and to take advantage of our findings to design new antibacterial agents.”

The research was supported by grants from the National Institutes of Health (CA009582, HL094296, AI091771, AI069233, AI073843, GM062122). Skaar holds the Ernest W. Goodpasture Chair in Pathology; Chazin holds the Chancellor’s Chair in Biochemistry and Chemistry and is director of the Vanderbilt Center for Structural Biology.
Contact:
Leigh MacMillan, (615) 322-4747
leigh.macmillan@vanderbilt.edu

Leigh MacMillan | EurekAlert!
Further information:
http://www.vanderbilt.edu

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 >>>