Navigation Links
Structure of bacterial nanowire protein hints at secrets of conduction

RICHLAND, Wash. -- Tiny electrical wires protrude from some bacteria and contribute to rock and dirt formation. Researchers studying the protein that makes up one such wire have determined the protein's structure. The finding is important to such diverse fields as producing energy, recycling Earth's carbon and miniaturizing computers.

"This is the first atomic resolution structure of this protein from an electrically conductive bacterial species, and it sets the foundation for understanding how these nanowires work," said structural biologist Patrick Reardon of the Department of Energy's Pacific Northwest National Laboratory. Reardon is the 2012 William R. Wiley Distinguished Postdoctoral Fellow at EMSL, the DOE's Environmental Molecular Sciences Laboratory at PNNL.

With the help of related structures on disease-causing bacteria, the researchers show that the protein's shape and form suggest possible ways for the bacteria to shuttle electrons along the nanowire. The results are reported in October in the Journal of Biological Chemistry.

"How to get electrons from the inside of bacteria to the outside is important for many different things, such as bacterial fuel cells, how carbon cycles through the environment and how to make new nanomaterials for applications like biocomputers," said Reardon.

Aromatic Therapy

Many bacterial species wave fingerlike projections along their bodies. The bacteria use these fingers, called pili, to adhere to surfaces or weave into films or recognize objects in the environment. A group of related bacteria makes these bendy, stretchy structures out of a protein called pilin, and an even smaller group uses these structures like electrical wires.

Researchers and engineers would like to take advantage of this wiring. Bacteria produce electrons while respiring and use the wires to run electrons out of their little bacterial bodies. Normally the electrons build up or break down minerals in rock, but the system can also be used to clean up toxic heavy metals or to run a bacterial fuel cell.

To better understand how pilins contribute to conduction, Reardon and NMR lead scientist Karl Mueller explored pilin from an electrically conducting bacteria known as Geobacter sulfurreducens.

Previous research on Geobacter's pilin -- PilA -- provided a big hint. PilA required certain spots along its length known as aromatic residues to conduct electricity. Without those aromatic residues where they were, Geobacter had no zip in its pili.

But proteins are like a long string that folds up into a compact three-dimensional shape. Without knowing the shape of pilin, it wasn't clear where the aromatic residues landed in space or how they contributed to electron shuttling.

Hop or Flow?

To find out, the researchers used NMR -- a technology similar to medical MRIs -- at EMSL to picture the shape of PilA.

On its own, PilA looks like a long skinny spring, with a slight kink about halfway up. The aromatic residues, which are bulky anyway, bulge along its length. But the protein by itself isn't enough to reveal how conduction works. Many pilin proteins work together to form a fiber, and Reardon and Mueller only had one.

Nor did the researchers have the whole fiber to put into the NMR instrument. To get more clues, Reardon borrowed the computer image of an assembled fiber from an unrelated species, the bacteria that cause gonorrhea. Gonorrhea's fiber does not conduct electricity nor does its pilin have as many aromatic residues. But its pilin has a similar shape to PilA, so using a computer program, Reardon overlaid PilA on its Gonorrhea cousins.

At this point, the aromatic residues clearly stood out.

"We get clusters of aromatic residues, and they wrap along the wire candy cane style," said Reardon.

But that just raised another question. If the electrons traveling along Geobacter's pilin are using these aromatic residues, they could be hopping from aromatic island to aromatic island. Alternatively, the aromatic residues could be close enough to pass the electrons through like a baton in a running race. Reardon and Mueller agree the single structure is not enough to choose between the two options.

The next step, Mueller said, is to purify the whole fiber from Geobacter microbes and determine the complete structure. The task is technologically challenging however because the fiber has to be grown within the bacteria themselves. Visualizing the whole fiber, though, will show the scientists if the fiber resembles islands in a stream more, or the streambed itself.


Contact: Mary Beckman
DOE/Pacific Northwest National Laboratory

Related biology news :

1. UMMS researchers answer century old question about 3D structure of mitotic chromosomes
2. Brain structure in post-traumatic stress disorder
3. Next-generation global e-infrastructure for taxon names registry
4. Model virus structure shows why theres no cure for common cold
5. CSHL is part of iPlant group awarded $50 million to create US biology cyberinfrastructure
6. $50 million NSF grant to advance cyberinfrastructure for big data in life sciences
7. Changes to symptom structure in DSM-5 support diagnosis of toddlers with autism spectrum disorder
8. Wistar scientists decipher structure of NatA, an enzyme complex that modifies most human proteins
9. AMP concerned about the structure and application of gap fill payment amounts
10. The genomes 3-D structure shapes how genes are expressed
11. Structure of cell signaling molecule suggests general on-off switch
Post Your Comments:
Related Image:
Structure of bacterial nanowire protein hints at secrets of conduction
(Date:11/4/2015)... York , November 4, 2015 ... a new market report published by Transparency Market Research "Home ... Growth, Trends and Forecast 2015 - 2022", the global home ... US$ 30.3 bn by 2022. The market is estimated ... forecast period from 2015 to 2022. Rising security needs ...
(Date:10/29/2015)... JOLLA, Calif. , Oct. 29, 2015  The ... a new report titled, "DNA Synthesis and Biosecurity: Lessons ... well the Department of Health and Human Services guidance ... issued in 2010. --> ... but it also has the potential to pose unique ...
(Date:10/29/2015)... BOSTON , Oct. 29, 2015  Connected health ... phenomena driving the explosion of technology-enabled health and wellness, ... his new book, The Internet of Healthy ... apps, sensors or smartphones even existed, Dr. Kvedar, vice ... model of health care delivery, moving care from the ...
Breaking Biology News(10 mins):
(Date:11/24/2015)... ... 24, 2015 , ... The United States Golf Association (USGA) today announced Dr. ... Award. Presented annually since 1961, the USGA Green Section Award recognizes an individual’s distinguished ... , Clarke, of Iselin, N.J., is an extension specialist of turfgrass pathology in ...
(Date:11/24/2015)... ... November 24, 2015 , ... International Society for Pharmaceutical ... the premier annual events for pharmaceutical manufacturing: 2015 Annual Meeting. The conference took ... hosted the largest number of attendees in more than a decade. , ...
(Date:11/24/2015)... , ... November 24, 2015 , ... The Academy of ... Interest Group (SIG), MultiGP, also known as Multirotor Grand Prix, to represent the First–Person ... few years. Many AMA members have embraced this type of racing and several new ...
(Date:11/24/2015)... FRANCISCO , Nov. 24, 2015  Twist ... announced that Emily Leproust, Ph.D., Twist Bioscience chief ... Jaffray Healthcare Conference on December 1, 2015 at ... Hotel in New York City. --> ... . Twist Bioscience is on Twitter. ...
Breaking Biology Technology: