PROFILE PROFILE Profile of Barbara Imperiali

Jennifer Viegas Science Writer

Barbara Imperiali’s research interests lie at plication of new techniques for synthesiz- the interface of chemistry and biology. She ing the complex and challenging structures interrogates biology with a chemical lexicon, of ansamycin . Her goal in joining using chemically driven strategies to provide the Masamune group was to become “a new insight into the fundamental processes molecule maker.” She explains, “Iwantedto of life (1). In doing so, she and her team have learn how to build molecules so that I could revealed diverse aspects of structure, later use this skill to probe biological systems. function, and design, and the role of I think that this was a great thing to be able to in cellular function and disease. do because it gave me a special talent in the Imperiali, a professor of Biology and way that I attacked biological problems.” Chemistry at the Massachusetts Institute of Imperiali also spent additional time as Technology, says, “I taught organic chemistry a postdoctoral associate in the Masamune to many unwilling students for 25 years,” laboratory, where she helped to launch a new adding that much of the first semester was biochemical project on the enzyme β-keto- spent trying to convince students that chem- thiolase. She gained experience in nearly istry was interesting. By the second semester, every aspect of enzyme biology, from ex- Barbara Imperiali. Photograph credit: many did indeed catch what she calls “the traction and purification to kinetic and Bachrach Photographers, Boston, MA. chemistry bug.” As a result, several genera- structural studies. Additional postdoctoral tionsofchemistsandotherscientistscredit work at with professor folding and trafficking, immunity, and many Imperiali for their inspiration. In recognition Robert Abeles decisively launched Imperiali’s other processes. “One aspect of protein gly- of her continuing achievements, Imperiali career as a biochemist and chemical biologist. cosylation that has fascinated me,” she says, was elected to the National Academy of From 1989 to 1999, Imperiali was at the “concerns how large glycan structures, which Sciences in 2010. California Institute of Technology as an as- are added during protein , affect sistant professor of chemistry, which later led protein folding, structure, and stability.” With Early Interest in Science to a chemistry professorship. “Ihavebeen Keith Rickert and Sarah O’Connor, both then ’ Imperiali was born on New Year s Day, 1957. fortunate to work in some great institutions graduate students at Caltech, she developed She grew up in , where she attended where inspiration abounds,” she says. Impe- experimental approaches to provide clues “ The Southbank School in Caterham. There riali was at Caltech during the time that on how cotranslational might were four different grades all crammed into chemist Dennis Dougherty was starting to trigger specific conformational changes in one room,” she says. Later, she attended work on applying unnatural amino acid mu- the early stages of protein biosynthesis and Coloma Grammar School in Croydon. The tagenesis in challenging problems focusing on therefore serve to nucleate future folding British grammar school system allows for the functions and interactions of ligand-gated events and the ultimate attainment of the early specialization in certain subjects and, membrane channels and receptors in the protein’s native folded state (2, 3). for Imperiali, there was no question that Xenopus (frog) oocyte system. She says, Using fluorescence resonance energy science was to be her focus. From the age of “I think that these studies represent real transfer and NMR studies, she and her col- 14 she dedicated much of her studies to works of art, and I present them every year leagues showed how the glycan structures learning about chemistry, physics, biology, when I teach .” that are appended to proteins uniquely elicit and math. She attended University College Doughertyandothersatthetimeinspired specific changes in the backbone London, where she earned a Bachelor of Imperiali to tackle important problems at the conformation that are reflected in the final Science degree in medicinal chemistry with chemistry–biology interface. folded states of the same peptide sequences in honors in 1979. the native proteins in which they are found. Return to MIT, Work on Protein In subsequent years, Imperiali and her team Molecule Maker Glycosylation tackled even more complicated glycosylation fi The same year, Imperiali made a signi cant Imperiali returned to MIT in 1999, becoming targets. For example, in 2003 they developed “ move. I shocked everyone at home by the Ellen Swallow Richards Professor of experiments to probe how glycosylation coming to the US,” she explains. The primary Chemistry. Throughout her career, she has might “protect” proteins from misfolding by draw was the Massachusetts Institute of worked on protein glycosylation, which studying a modular domain of a prion pro- Technology (MIT), where she earned a PhD involves the enzyme-catalyzed modification tein (3). She also helped to develop a system in synthetic organic chemistry. Her PhD of proteins with complex carbohydrates to mentor was organic chemist Satoru Masa- alter their structure or function. Glyco- This is a Profile of a recently elected member of the National mune. During her doctoral work Imperiali proteins are abundant in living organisms, Academy of Sciences to accompany the member’s Inaugural Article, was involved in the development and ap- serving important functions related to protein 10.1073/pnas.1320852110.

www.pnas.org/cgi/doi/10.1073/pnas.1321020110 PNAS Early Edition | 1of2 Downloaded by guest on October 1, 2021 investigating how glycosylation influences not oration with the group of Michael Yaffe of the enzymes in the pathways that they only the thermodynamic stability of proteins at MIT (6). wanted to study, because the enzymes all but also the mechanics of how it affects the Her group also developed a fluorescence- required detergent solubilization for purifi- process of reaching the folded state (4). basedmethodforsensingpeptideandpro- cation and analysis. Six years ago, it was not A source of inspiration at MIT has been tein (addition of a phos- possible to dissect the roles of the linear the ribonucleotide reductase work of bio- phate group to a molecule) that could be polyprenols in the sequential pathway pro- chemist JoAnne Stubbe. Imperiali explains, used to monitor protein kinase activity. cesses in a native membrane environment. “The rigor and creativity with which she has Kinases are extremely important targets Over the last few years, however, Imperiali tackled understanding the fundamental because they are involved in coordinating and her team overcame most of those chal- properties and reactivity of this central en- nearly all cellular activity. They often mal- lenges and are now able to simultaneously zyme highlight the power of chemical and function in disease states, such as cancer. assess the interactions and activities of the physical approaches in illuminating the Through interactions with colleagues at both polyprenyl-linked substrates, enzymes, and details of really complex processes and drive MIT and other universities, Imperiali and lipid bilayer. She says, “To me, this body of me to take on the investigation of challenging her team fine-tuned the approach into a work finally establishes an experimental sys- ” problems in my own work. method that can screen kinase inhibitors tem that I believe will enable us to get to the fi and pro le kinase activities in cell and tissue real basis for the conservation of extended Dissection of an Archaeal Protein “ lysates (7, 8). The approach that we de- linear polyprenols in cellular glycoconjugate Pathway veloped has been commercialized, and we biosynthesis pathways.” Imperiali’s interest in the intricacies of pro- are now looking towards ways to further Imperiali’s work, looking at proteins in tein glycosylation pathways led her and her development of the methods for diagnostic their living context, has applications for colleagues to take on the challenge of dis- ” applications, she says. everything from drug development to diag- secting the biochemical details of an archaeal nostics. Her achievements have led to many pathway (5). Archaea are single-celled mi- Glycan Assembly honors, including the Protein Society Emil T. croorganisms that often live in extreme Imperiali’s Inaugural Article speaks to a re- Kaiser Award and the American Chemical conditions, such as at high temperatures or curring theme in cellular glycan assembly Society Breslow Award. She was elected to extreme acidity. Scientists have long puzzled processes (9). Specifically, linear, long chain the American Academy of Arts and Sci- over how the biochemical pathways of these polyprenols are omnipresent molecular microorganisms might be adapted to work components in the biosynthetic pathways ences in 2001 and was admitted as a “ fi responsible for the assembly of essential Fellow of the Royal Society of Chemistry in under such conditions. She says, At rst it ’ seemed that the archaeal pathway that we glycoconjugates (carbohydrates covalently 2004. She earned Caltech and MIT s highest linked with other chemical species) in- honors for teaching: in 1998, Imperiali re- were investigating was likely to be very sim- ’ ilar to the corresponding pathway in other cluding peptidoglycan and N-linked gly- ceived Caltech s Richard P. Feynman Award domains of life, but we started to find in- coproteins. Despite their highly conserved for Excellence in Teaching, and in 2003, she consistencies that suggested that there might presence in all domains of life, the role of was named a Margaret McVicar Faculty be variations in the pathways for archaeal the extended polyprenyl groups in the dy- Fellow in recognition of contributions to organisms that tend to exist under more namics of membrane-bound glycan assembly education at MIT. extreme conditions.” pathways remains a mystery. “Certainly these Collaboration and teaching remain two of Imperiali and her team documented key components act as membrane anchors, but her greatest rewards. Regarding the former, “ differences in the specific biochemical details the physical length of the polyprenyl groups she says, I really enjoy intense collaborative of the individual steps. To this day, she and the specific geometric features of the efforts where one has to stretch to cross and her team are still puzzling over the structures strongly suggest a far more so- boundaries and understand how expertise findings, but she says, “I believe that there phisticated role,” Imperiali says. from a different discipline can shed light on is little doubt that there must be some good In 2007, Imperiali and her team estab- a challenging problem that you have studied reason—perhaps from an evolutionary per- lished the foundation for this current work using techniques that you are familiar and spective—for the observed archaeal varia- by assembling the enzymes and substrates comfortable with.” Imperiali’spursuitsinthe tions of the glycosylation pathway that we required to ask questions about the structures laboratory are inseparable from her work in have characterized.” and functions of the polyprenol linked sub- the classroom, which helps to fuel her re- strates (10). The researchers were frustrated, search projects. She explains, “I love to teach! Measuring and Manipulating however, by the membrane-associated nature I get so much energy from it.” Biochemical Processes Another major component of Imperiali’s collaborative research involves studies con- 1 Imperiali B (2009) Interrogating biology with a chemical lexicon. 6 Nguyen A, Rothman DM, Stehn J, Imperiali B, Yaffe MB (2004) Nat Chem 1(1):9–10. Caged phosphopeptides reveal a temporal role for 14-3-3 in G1 arrest cerning the design, development, and appli- 2 Imperiali B, Rickert KW (1995) Conformational implications of and S-phase checkpoint function. Nat Biotechnol 22(8):993–1000. cation of chemical approaches for measuring asparagine-linked glycosylation. Proc Natl Acad Sci USA 92(1): 7 Shults MD, Janes KA, Lauffenburger DA, Imperiali B (2005) A and manipulating biochemical processes. She 97–101. multiplexed homogeneous fluorescence-based assay for protein 3 Bosques CJ, Imperiali B (2003) The interplay of glycosylation and kinase activity in cell lysates. Nat Methods 2(4):277–283. and her team constructed chemically caged disulfide formation influences fibrillization in a prion protein 8 Stains CI, et al. (2012) Interrogating signaling nodes involved in cellular phosphoamino acid building blocks for as- fragment. Proc Natl Acad Sci USA 100(13):7593–7598. transformations using kinase activity probes. Chem Biol 19(2):210–217. 4 Chen MM, et al. (2010) Perturbing the folding energy 9 Hartley MD, Schneggenburger PE, Imperiali B (2013) Lipid sembly into both and proteins. They landscape of the bacterial immunity protein Im7 by site-specific bilayer nanodisc platform for investigating polyprenol-dependent used this ability to rapidly and selectively N-linked glycosylation. Proc Natl Acad Sci USA 107(52): enzyme interactions and activities. Proc Natl Acad Sci USA, 10.1073/ release bioactive phosphopeptides and exploit 22528–22533. pnas.1320852110. 5 Larkin A, Chang MM, Whitworth GE, Imperiali B (2013) 10 Chen MM, et al. (2007) Polyisoprenol specificity in the these reagents in cellular studies focusing on Biochemical evidence for an alternate pathway in N-linked Campylobacter jejuni N-linked glycosylation pathway. DNA damage and cell cycle control, in collab- glycoprotein biosynthesis. Nat Chem Biol 9(6):367–373. 46(50):14342–14348.

2of2 | www.pnas.org/cgi/doi/10.1073/pnas.1321020110 Viegas Downloaded by guest on October 1, 2021