Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Solving streptide from structure to biosynthesis

18.05.2015

Bacteria speak to one another using peptide signals in a soundless language known as quorum sensing. In a step towards translating bacterial communications, researchers at Princeton University have revealed the structure and biosynthesis of streptide, a peptide involved in the quorum sensing system common to many streptococci.

"It's extremely rare for one research group to do both natural products discovery and mechanistic enzymology," said Leah Bushin, a member of the Seyedsayamdost lab and co-first author on the article published on April 20 in Nature Chemistry. Bushin worked on elucidating the structure of streptide as part of her undergraduate senior thesis project and will enter Princeton Chemistry's graduate program in the fall.


In a step towards translating bacterial communications, researchers at Princeton University have revealed the structure and biosynthesis of streptide, a peptide involved in the quorum sensing system common to many streptococci.

Credit: Seyedsayamdost lab

To explore how bacteria communicate, first she had to grow them, a challenging process in which oxygen had to be rigorously excluded. Next she isolated the streptide and analyzed it using two-dimensional (2D) nuclear magnetic resonance (NMR) spectroscopy, a technique that allows scientists to deduce the connections between atoms in a molecule by pulsing their nuclei with powerful magnets to pulse atomic nuclei.

The experiments revealed that streptide contained an unprecedented crosslink between two unactivated carbons on lysine and tryptophan, constituting a new class of macrocyclic peptides. "We didn't think it would be as cool as a carbon-carbon bond between two amino acid side chains, so it was definitely a surprise." said Bushin.

To figure out how this novel bond was being formed, the researchers took a closer look at the gene cluster that produced streptide. Within the gene cluster, they suspected a radical S-adenosyl methionine (SAM) enzyme, which they dubbed StrB, could be responsible for this unusual modification.

"Radical SAM enzymes catalyze absolutely amazing chemistries," said Kelsey Schramma, a graduate student in the Seyedsayamdost lab and co-first author on the article. "There are over 48,000 radical SAM enzymes, but only about 50 have been characterized and just a dozen or so studied in detail," she said.

To probe the enzyme's role in making streptide, the researchers created a mutated version of the bacteria lacking the strB gene. The mutant failed to produce streptide, confirming that the StrB enzyme was significant and warranted further study.

Schramma determined that in order to function properly, the StrB enzyme required some key components: the pre-crosslinked substrate, which she prepared synthetically, cofactor SAM, reductant, and two iron-sulfur (Fe-S) clusters carefully assembled in the protein interior. The team then showed that one of the FeS clusters reductively activated one molecule of SAM, kicking off a chain of one-electron (radical) reactions that gave rise to the novel carbon-carbon bond.

"The synergy between Leah and Kelsey was great," said Mohammad Seyedsayamdost, an assistant professor of chemistry at Princeton who led the research team. "They expressed interest in complementary aspects of the project and the whole ended up being greater than the sum of its parts," he said.

Their efforts included not only chemical and biological approaches, but also theoretical computational studies. While the 2D NMR experiments revealed the flat structure of streptide, its three-dimensional conformation was still unknown.

"Since the crosslink had never been reported, we had to code the modification into the program, which took a bit of creativity," Bushin said. After corresponding with the software creator, they were able to confidently assign a key residue in the macrocycle with the S-configuration.

Future work will target streptide's biological function -- its meaning in the bacterial language -- as well as confirming its production by other streptococcal bacteria strains.

"What we have revealed is a new and unusual mechanism that nature uses to synthesize macrocyclic peptides. There is a lot of novel chemistry to be discovered by interrogating bacterial secondary metabolite biosynthetic pathways," Seyedsayamdost said.

###

Read the full article here:

Schramma, K. R.; Bushin, L. B.; Seyedsayamdost, M. R. "Structure and biosynthesis of a macrocyclic peptide containing an unprecedented lysine-to-tryptophan crosslink." Nature Chemistry, 2015, 7, 431.

This work was supported by the National Institutes of Health (grant no. GM098299), and by Princeton University start-up funds.

Media Contact

Tien Nguyen
tienn@princeton.edu
609-258-6523

 @Princeton

http://www.princeton.edu 

Tien Nguyen | EurekAlert!

Further reports about: SAM amino acid bacteria bacterial biological function biosynthesis modification nuclei peptides

More articles from Life Sciences:

nachricht Multi-institutional collaboration uncovers how molecular machines assemble
02.12.2016 | Salk Institute

nachricht Fertilized egg cells trigger and monitor loss of sperm’s epigenetic memory
02.12.2016 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>