A 40-year search for a gene that causes some one-celled sea creatures to flash at night and is also found in others that produce deadly red tides, has been successfully culminated by a group of scientists led by Thomas E. DeCoursey, PhD, professor of biophysics and physiology at Rush University Medical Center.
The gene, discovered in a tiny marine organism called a dinoflagellate (Karlodinium veneficum), controls voltage-gated proton channels, which, in addition to triggering luminescence in certain single-cell sea creatures, activate many important biological mechanisms in other species, including humans.
Results of the study by DeCoursey, Susan M. E. Smith and co-researchers were published in the October 17, 2011 issue of the Proceedings of the National Academy of Sciences. The study was funded in part by grants from the National Science Foundation and the National Institutes of Health.
The existence of a voltage-gated proton channel in bioluminescent dinoflagellates was proposed in 1972 by J. Woodland Hastings, a co-author on the current study, and his colleague Margaret Fogel. They hypothesized that proton channels helped trigger the flash by activating luciferase, an enzyme that helps produce luminescence. But until now, the genetic code responsible for the proton channels in dinoflagellates had not been identified, although it had been decrypted in humans, mice, algae and sea squirts.
Voltage-gated proton channels are extremely versatile. In humans, they are involved in several basic biological processes, including release of histamine in basophils, a type of white blood cell. Proton channels also play a role in the production of reactive oxygen species such as hydrogen peroxide that kill bacteria in phagocytes, another kind of white blood cell, and in maturation of sperm immediately before fertilization.
In the current study, DeCoursey and co-researchers mined the gene sequence library of a K veneficum dinoflagellate and found a gene named kHv1 that is similar to those already known to code for proton channels in other species. Not surprisingly, there were many differences in the make-up of the proton channel molecules in humans and tiny sea creatures, but the most important parts of the molecules turned out to be almost identical. Electrophysiologic tests confirmed that the genetically coded protein was indeed a proton channel – but one with an unprecedented quality.
Proton currents in K veneficum differ from all known proton currents in having large inward currents—a result of the channels opening at membrane potentials about 60 mV more negative than in other species, the researchers found.
“Vertebrate proton channels open to allow acid extrusion, while dinoflagellate proton channels open to allow proton influx into a cell’s cytoplasm, making the channel ideally suited to trigger bioluminescence,” DeCoursey explained.
When dinoflagellates floating in water are mechanically stimulated by movement, an impulse (action potential) is sent along the membrane of an internal compartment called a vacuole. Clustered along the inside of this membrane are tiny pockets called scintillons, containing a combination of luciferin and luciferase – proteins that are able to produce a light flash under the right circumstances. The inside of the vacuole compartment is very acidic and has an abundance of protons.
As the electric impulse travels along the membrane, it causes the voltage-sensitive proton channels to open. Protons then flow from the vacuole into the scintillon, where they react with the luciferase and a flash of light results.
In nonbioluminescent mixotrophic species like K veneficum, proton influx might be involved in prey digestion (e.g., signaling prey capture) or prey capture (e.g., extrusion of stinging trichocysts).
Co-investigator Susan Smith carried out a phylogenetic analysis of known Hv1 sequences, finding high sequence diversity among the single-celled species and among invertebrates. She interpreted this finding to suggest the possibility of other novel functions of Hv1 in these species.
“As in multicellular organisms, ion channels in dinoflagellates play various roles in regulating basic life functions, which make them targets for controlling dinoflagellate populations and behavior,” the authors suggested.
Future research will show whether targeting proton channels might give us a handle on controlling dinoflagellate blooms that cause deadly red tides and are responsible for massive fresh kills. Certain dinoflagellate species produce some of the most deadly poisons known, such as saxitoxin, a neurotoxin 100,000 times more potent than cocaine. Paralytic shellfish poisoning occurs in humans who eat shellfish that have consumed toxic dinoflagellates.
In addition to DeCoursey, Smith (Emory School of Medicine) and Hastings (Harvard University), the authors of this paper include Deri Morgan, Boris Musset and Vladimir V. Cherny of Rush University Medical School, and Allen R. Place of the University of Maryland Center for Environmental Sciences.
Deb Song | EurekAlert!
Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery
20.01.2017 | GSI Helmholtzzentrum für Schwerionenforschung GmbH
Seeking structure with metagenome sequences
20.01.2017 | DOE/Joint Genome Institute
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
20.01.2017 | Awards Funding
20.01.2017 | Materials Sciences
20.01.2017 | Life Sciences