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 Wintering ducks connect isolated wetlands by dispersing plant seeds
22.02.2017 | Utrecht University

nachricht Warming ponds could accelerate climate change
21.02.2017 | University of Exeter

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

NASA's fermi finds possible dark matter ties in andromeda galaxy

22.02.2017 | Physics and Astronomy

Wintering ducks connect isolated wetlands by dispersing plant seeds

22.02.2017 | Life Sciences

Impacts of mass coral die-off on Indian Ocean reefs revealed

21.02.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>