Inside the Box
University of Iowa
Published September 17, 2013
They say the shoes make the man. For Mishtu Dey, assistant professor of chemistry at the University of Iowa, the shoes made the science.
In 2007, during the last year of her postdoc at the University of Michigan, Dey told her mentor, Steve Ragsdale, that she wanted to crystallize the enzyme she was studying, methyl-coenzyme M reductase (mcr), the only enzyme found in nature that produces methane. Ragsdale, who isn't a crystallographer, gave her the go ahead. "He didn't think I'd actually do it," she says.
The trouble was that oxygen inactivates mcr so that it won't take up the substrates or produce the methane product. "If I don't keep oxygen out of the system, I'll end up with a dead enzyme," says Dey.
So Dey had to figure out how to do anaerobic crystallography on her own in a lab that wasn't even set up for basic crystallography. She set up crystal trays in an oxygen-free glove box and pulled a microscope inside. To see through the eyepiece, she had to tilt the scope towards the plexiglass and look in from the outside. "I had a certain size heel on the shoes I wore to make the height perfect for me to see through," she says.
Heels and all, it was worth it. Day became the first person to crystallize mcr in one of its many redox-active form. "That was really exciting for me," says Dey, who in her lab in Iowa is now trying to crystallize the active form.
Dey had originally trained as a chemist at the Indian Institute of Technology in Mumbai, where in graduate school she worked on supramolecular host-guest chemistry. She had learned crystallography as part of her work designing and synthesizing biomimetic small molecule complexes that could be used for glucose sensing and monitoring in medical devices.
During that time, she found herself asking a pivotal question: Why not work with real enzymes? The question led her to the Ragsdale lab. "Deciding to transition to biochemistry was the biggest decision of my career," she says.
Initially, the switch presented a steep learning curve. "Synthesizing molecules in flasks is a different mindset from growing microbes in a fermenter," she says.
By the time she'd gotten the hang of it, her interest in crystallography had resurfaced, inspiring her to crystallize mcr. Once she had the crystals, she traveled to Chicago from Ann Arbor for days at a time to visit the synchrotron and collect the data.
While exciting, the work was also frustrating because Dey wasn't able to solve the structures on her own. "I decided that if I'm doing so much crystallography, why not go to a crystallography lab and learn the last bit, how to work with the data," she says.
Dey moved to the lab of Catherine Drennan at MIT and worked on another anaerobic enzyme, hydroxypropylphosphonic acid epoxidase (HppE). In 2013, Dey's findings that this antibiotic biosynthetic enzyme's mechanism of action involved an unprecedented reaction were published in Nature.
In 2011, Dey moved to the University of Iowa to start her own lab. "I was looking for a research university with a medical school on campus," she says. She envisioned collaborating with medical researchers and doing work in mammalian systems to study human diseases.
That vision has already materialized. Today, one of the main focuses in Dey's lab is working with human cancer cell lines to study oxygen-sensing metallo-enzymes. These enzymes regulate genetic programs in response to hypoxia, a common feature deep inside tumors. In this work, she combines crystallography with techniques from biochemistry and spectroscopy to understand these enzymes.
The crystallography work at Iowa is easier now that she has introduced the university's protein crystallography core and other crystallography labs to SBGrid. Yet one of her biggest challenges remains the same. "Anaerobic crystallography was really challenging 10 years back, and its the same challenge now," she says. "If you're doing any redox biology or biochemistry, oxygen is always a concern."
-- Elizabeth Dougherty