New mechanism unlocked for evolution of green fluorescent protein


January 21, 2015

A primary challenge in the biosciences is to understand the way major evolutionary changes in nature are accomplished. Sometimes the route turns out to be very simple. An example of such simplicity is provided in a new publication by a group of ASU scientists.

They show, for the first time, that a hinge migration mechanism, driven solely by long-range dynamic motions, can be the key for evolution of a green-to-red photoconvertible phenotype in a green fluorescent protein (GFP). S. Banu Ozkan and Rebekka Wachter Download Full Image

Rebekka Wachter, a professor in ASU’s Department of Chemistry and Biochemistry and the College of Liberal Arts and Sciences, is an expert in the field of structural characterization of GFP-like proteins. The present study is the culmination of eight years of intense effort in her laboratory.

The work, just published in the high impact journal Structure, involves collaborations with S. Banu Ozkan, from the Center for Biological Physics in the Department of Physics at ASU, and evolutionary biologist Mikhail Matz of the University of Texas.


Green fluorescent protein was first isolated from the jellyfish Aequorea victoria, which drifts with the currents off the west coast of North America. It was discovered that this protein glowed bright green under ultraviolet light. This phenomenon has found many creative applications in the biosciences.


The protein has been utilized as an extremely valuable luminous genetic tag for various biological phenomena. Using green fluorescent protein one can observe when proteins are made and where they go. This is done by joining the GFP gene to the gene of the protein of interest so that when the protein is made it will have GFP hanging off it. Since GFP fluoresces, one can shine light at the cell and wait for the distinctive green fluorescence associated with GFP to appear. The ability of some GFPs to turn red upon prolonged illumination makes them invaluable probes in super resolution fluorescence microscopy applications. This is where the current study is of most value.

To fluoresce, GFP-like proteins must adopt a compact barrel-like shape.  The light-triggered red phenotype may have arisen from a common green ancestor by a reversal of firm and soft regions located in opposite corners of the beta-barrel fold.

Although six crystal structures of reconstructed ancestral Kaede-type proteins indicate that the structure is highly conserved, analysis of chain flexibility by Molecular Dynamics and perturbation response scanning, performed in the group of S. Banu Ozkan has shown that the individual flexibility of each position (i.e. structural dynamics) alters throughout the evolution of green-to-red photo conversion. Thus this study suggests that green-to-red photoconversion may have arisen from a common green ancestor by the  shift of the rigid corner near  the chromophore to the opposite corner of beta-barrel.

“For the first time, this work establishes a direct experimental link between protein phenotypic change and collective dynamics without any external trigger, such as substrate, product or effector binding,” explains Wachter. “Based on structural, computational and kinetic data, we propose a novel photoconversion mechanism that provides a plausible path for the irreversible acquisition of red fluorescence.”

In spite of intense efforts in a number of laboratories worldwide, the mechanism of photoconversion of Kaede-type proteins has remained largely enigmatic. The present work sheds light on structural, dynamic and mechanistic features that must be considered when engineering improved fluorescent probes for super-resolution microscopy applications.

ASU's Department of Chemistry and Biochemistry ranks 6th worldwide for research impact (gauged by the average cites per paper across the department for the decade ending in the 2011 International Year of Chemistry), and in the top eight nationally for research publications in the journals Science and Nature. The department’s strong record in interdisciplinary research is also evidenced by its 31st national ranking by the National Science Foundation in total and federally financed higher education research and development expenditures in chemistry.


Source: Rebekka Wachter, Rebekka.Wachter@asu.edu

Jenny Green

Clinical associate professor, School of Molecular Sciences

480-965-1430

Family honors sister's UN service with artwork donation to ASU


January 21, 2015

An island shook. A nation bled. A sister lost her life.

On Jan. 12, 2010, a catastrophic magnitude-7.0 earthquake centered near the Haitian capital of Port-au-Prince leveled residences and businesses, and more than 200,000 people lost their lives. Within two weeks of the massive temblor, 45 aftershocks of magnitude-4.5 or greater had been recorded. painting of a woman on a swing Download Full Image

Vital infrastructure was damaged or destroyed. Hospitals; air, sea and land transport facilities; and communication systems ceased to operate. Devastation was everywhere. Of the lives cut short that afternoon was Nicole Valenta, a United Nations best practices officer based in the capital city. The headquarters of the U.N.’s stabilization mission where she worked collapsed, killing many, including mission chief Hédi Annabi.

Five years later, out of the country’s ruin and a family’s sorrow, comes a philanthropic gift of Haitian art to Arizona State University’s New College of Interdisciplinary Arts and Sciences. Nicole Valenta’s younger and only brother, Marcel Valenta, and his parents, Anne and Gunter, donated the 15-piece collection of modern paintings in her memory.

Included in the gift is artwork by Préfète Duffaut, an iconic Haitian painter who was commissioned in 1950 to paint murals in the interior of the Cathedral of Sainte Trinité, which was destroyed in the 2010 quake, as well as Nelson Woodley, who learned from the widely collected St. Louis Blaise, and is a celebrated painter in his own right.

“My sister always had an interest in all kinds of artistic expression – music, dancing, painting, photography, architecture – and she dabbled in most of them herself,” says Marcel Valenta, who serves as general counsel for the ASU Foundation for A New American University.

Nicole collected the paintings during her four years (2007-2010) as the U.N.’s conduct and discipline officer in Haiti and ultimately chief of the international organization’s best practices unit.

Her career with the U.N. began in 2000 and was the culmination of a lifelong dream to help others. Appointed associate officer with the U.N. Institute for Training and Research in Geneva, she was transferred to New York in 2002, where she was responsible for trainings related to international affairs and diplomacy. After studying law at New York University and passing the New York state bar exam, she accepted a U.N. field position in the Democratic Republic of Congo, serving as a human rights officer in Kinshasa and later in Beni Ituri.

“Her taste was broad and inclusive, and I hope my donation helps add an interesting piece to the puzzle that this rich, colorful ASU community already is,” says Marcel. “If only a fraction of the students viewing these paintings start dreaming about an international career and then in fact embark on the path of pursuing one, this donation will have achieved more than my sister would have ever dared to hope for.”

Haitian art, first developed during the late 18th and early 19th centuries, reflects the island country’s African roots and features Native American and European aesthetic and religious influences. “Haitian art is what makes the international eye see us," said Joseph Gaspard, of Musée d’Art Haitien du Collège St Pierre, in an interview with the Los Angeles Times just weeks following the earthquake. "Every Haitian is an artist. Art, it is us, it's what we are."

Marcel says he chose to donate the artworks to New College because of the school’s inclusive and multi-perspective focus that mirrors his sister’s character. “In its interdisciplinary approach to education, New College, in my view, helps students develop the versatility and open-mindedness necessary to succeed in an environment as multi-faceted and diverse as the U.N.’s. Philosophically, these two institutions have a lot in common. Having my sister’s life serve as even the slightest inspiration for an international career for any of the New College graduates would have made her so happy.

“I also hope the paintings can serve as a first step in building a relationship between New College and the United Nations,” Marcel adds. “Both organizations are about interdisciplinary outreach, inclusion and breadth. They both seek minds who are just as confident repairing a Diesel engine as they are understanding the historic perspective of a tribal dispute in northeastern Congo.”

Marcel’s gift of artwork, and the contributions of those who support New College and ASU through collections, real estate and physical assets, are critical to the continued advancement of the university and the learning experience of its students, says Marlene Tromp, vice provost at ASU’s West campus and New College dean.

“We value the importance of this extraordinary artwork that the Valenta family has donated in Nicole’s memory,” says Tromp, a professor of English and women and gender studies. “We strive to be good stewards of all the gifts we receive, and in-kind gifts such as this help us offer truly unique learning experiences for our students, as well as to maximize our resources for serving students and the community. This artwork will play a vital role in connecting students to a world beyond the classroom, and we are honored to display it for all of ASU to enjoy.”

“Nicole loved people and collected art based on her love for people,” says Marcel. “She never viewed art through a curator’s eye, and didn’t care what others thought about the art or its market value. Her collection, to me, is a sign of her incredible ability to immerse herself in different cultures and to truly be intrigued by the people in the places she lived in.

“My donation should be an example of how ASU can serve as an incredible amplifier to any type of philanthropy,” Marcel adds. “Everyone, I believe, always has a chance to change their trajectory in life, set new goals and succeed in achieving them. But one of the best opportunities in life to break through ceilings, positively impact one’s trajectory and do things one thought one couldn’t do is probably during the four years of college. That’s powerful stuff, and for anyone who is in the position to be generous, contributing to an organization like ASU is a great opportunity to make a difference in people’s lives and positively impact societal change at a meaningful scale.”

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