Findings in redox biology: From H2O2 to oxidative stressMy interest in biological chemistry proceeded from enzymology in vitro to the study of physiological chemistry in vivo. Investigating biological redox reactions, I identified hydrogen peroxide (H2O2) as a normal constituent of aerobic life in eukaryotic cells. This finding led to developments that recognized the essential role of H2O2 in metabolic redox control. Further research included studies on GSH, toxicological aspects (the concept of “redox cycling”), biochemical pharmacology (ebselen), nutritional biochemistry and micronutrients (selenium, carotenoids, flavonoids), and the concept of “oxidative stress.” Today, we recognize that oxidative stress is two-sided.
Lucky, times ten: A career in Texas scienceOn January 21, 2017, I received an E-mail from Herb Tabor that I had been simultaneously hoping for and dreading for several years: an invitation to write a “Reflections” article for the Journal of Biological Chemistry. On the one hand, I was honored to receive an invitation from Herb, a man I have admired for over 40 years, known for 24 years, and worked with as a member of the Editorial Board and Associate Editor of the Journal of Biological Chemistry for 17 years. On the other hand, the invitation marked the waning of my career as an academic scientist.
My journey in the discovery of nucleotide sugar transporters of the Golgi apparatusDefects in protein glycosylation can have a dramatic impact on eukaryotic cells and is associated with mental and developmental pathologies in humans. The studies outlined below illustrate how a basic biochemical problem in the mechanisms of protein glycosylation, specifically substrate transporters of nucleotide sugars, including ATP and 3′-phosphoadenyl-5′-phosphosulfate (PAPS), in the membrane of the Golgi apparatus and endoplasmic reticulum, expanded into diverse biological systems from mammals, including humans, to yeast, roundworms, and protozoa.
An exploration of bioactive peptides: My collaboration with Ervin G. ErdösThis paper provides a brief historical sketch of the science of biologically active peptides. It also offers the story of how Ervin G. Erdös, a pioneer in the study of metabolism of various peptides, influenced me through collaborations that span many years. I worked in Dr. Erdös's research laboratories in Oklahoma City, Dallas, and Chicago, and we shared research interests through visits across the Atlantic between the former Yugoslavia and the United States. Among other findings, we discovered angiotensin-converting enzyme in the retina, which opened up a new research direction for many scientists interested in serious ocular diseases.
Membrane protein serendipityMy scientific career has taken me from chemistry, via theoretical physics and bioinformatics, to molecular biology and even structural biology. Along the way, serendipity led me to work on problems such as the identification of signal peptides that direct protein trafficking, membrane protein biogenesis, and cotranslational protein folding. I’ve had some great collaborations that came about because of a stray conversation or from following up on an interesting paper. And I’ve had the good fortune to be asked to sit on the Nobel Committee for Chemistry, where I am constantly reminded of the amazing pace and often intricate history of scientific discovery.
From masochistic enzymology to mechanistic physiology and diseaseThe pioneering work of Eugene Kennedy in the 1950s established the choline pathway for phosphatidylcholine (PC) biosynthesis. However, the regulation of PC biosynthesis was poorly understood at that time. When I started my lab at the University of British Columbia in the 1970s, this was the focus of my research. This article provides my reflections on these studies that began with enzymology and the use of cultured mammalian cells, and progressed to utilize the techniques of molecular biology and gene-targeted mice.
Understanding phospholipid function: Why are there so many lipids?In the 1970s, phospholipids were still considered mere building blocks of the membrane lipid bilayer, but the subsequent realization that phospholipids could also serve as second messengers brought new interest to the field. My own passion for the unique amphipathic properties of lipids led me to seek other, non-signaling functions for phospholipids, particularly in their interactions with membrane proteins. This seemed to be the last frontier in protein chemistry and enzymology to be conquered.
Riding the metalloproteinase roller coasterTo many of us in the field, working on matrix metalloproteinases (MMPs) has felt like riding a roller coaster, traveling through times of both excitement and despair. I was fortunate to join the ride when it was a mere carousel of three activities thought to target the proteins that comprise the extracellular matrix (ECM). New technologies brought the thrills of discovery as we uncovered specific proteinase genes and defined specialized activities in different cellular processes. The MMPs and the sister families of “a disintegrin and metalloproteinase” (ADAMs), ADAMs with thrombospondin domains (ADAM-TS), and Astacins are now recognized as key signaling “scissors” that drive rapid changes in a plethora of cellular pathways.
Traversing the RNA worldAn invitation to write a “Reflections” type of article creates a certain ambivalence: it is a great honor, but it also infers the end of your professional career. Before you vanish for good, your colleagues look forward to an interesting but entertaining account of the ups-and-downs of your past research and your views on science in general, peppered with indiscrete anecdotes about your former competitors and collaborators. What follows will disappoint those who await complaint and criticism, for example, about the difficulties of doing research in the 1960s and 1970s in Eastern Europe, or those seeking very personal revelations.
Investigating Viruses during the Transformation of Molecular BiologyThis Reflections article describes my early work on viral enzymes and the discovery of mRNA capping, how my training in medicine and biochemistry merged as I evolved into a virologist, the development of viruses as vaccine vectors, and how scientific and technological developments during the 1970s and beyond set the stage for the interrogation of nearly every step in the reproductive cycle of vaccinia virus (VACV), a large DNA virus with about 200 genes. The reader may view this article as a work in progress, because I remain actively engaged in research at the National Institutes of Health (NIH) notwithstanding 50 memorable years there.
Liberating Chiral Lipid Mediators, Inflammatory Enzymes, and LIPID MAPS from Biological GreaseIn 1970, it was well accepted that the central role of lipids was in energy storage and metabolism, and it was assumed that amphipathic lipids simply served a passive structural role as the backbone of biological membranes. As a result, the scientific community was focused on nucleic acids, proteins, and carbohydrates as information-containing molecules. It took considerable effort until scientists accepted that lipids also “encode” specific and unique biological information and play a central role in cell signaling.
Finding ChannelsThis Reflections article tells the story of the early work in my laboratory at the University of Washington that led to discovery of the sodium and calcium channel proteins, followed by a briefer description of the structure and function of these remarkable membrane proteins that has emerged from research in my laboratory and others over many years. I began my scientific career as an undergraduate chemistry major at Brown University, where my senior thesis research with Dr. Joseph Steim introduced me to the mysteries of membrane proteins in 1967–1968.
In Pursuit of Genes of Glucose MetabolismIf you don't know where you're going, you might wind up someplace else—Yogi Berra
Heme and II was born in Mexico City in 1942 into a family immersed in literature and art, but with no proclivity toward the sciences. My father, Bernard Ortiz de Montellano, was a poet of some standing in Mexico, an academic, and the editor of a magazine called Contemporaneos, which reported on current literary and artistic trends. In this last capacity, he was well related to the cadre of artists and writers, such as Diego Rivera and Rufino Tamayo, who were bringing Mexico into the world art forum. My mother was an adventurous American from Missouri who had ventured into Mexico in wild and woolly post-revolutionary days to earn a master's degree in Spanish and stayed to marry one of her professors.
“Modifying” My Career toward Chromatin BiologyLike most, if not all, graduate students, I faced some hurdles along the way that seemed higher than the rest. In my doctoral program at Indiana University in Bloomington, a required, but to me dreaded, seminar course in genetics stood in the way. It was a small class that was directed by a professor well known for demanding painful excellence from all those who enrolled. My self-confidence was shaky, but I knew that I did not want to strike out.
Transient Intermediates in Enzymology, 1964–2008I was born to John and Inez Frey in Plain City, Ohio, on November 14, 1935, and I received primary and secondary education in the local public schools. My father worked in seasonally complementary trades as a sheep shearer and painting contractor. He hired me in the contracting business during school breaks through junior and senior high school and college. He instilled in me the values of hard work and uncompromising honesty, which have served me well. My mother managed the local office of the General Telephone Company.
Radicals in Berkeley?In a previous autobiographical sketch for DNA Repair (Linn, S. (2012) Life in the serendipitous lane: excitement and gratification in studying DNA repair. DNA Repair 11, 595–605), I wrote about my involvement in research on mechanisms of DNA repair. In this Reflections, I look back at how I became interested in free radical chemistry and biology and outline some of our bizarre (at the time) observations. Of course, these studies could never have succeeded without the exceptional aid of my mentors: my teachers; the undergraduate and graduate students, postdoctoral fellows, and senior lab visitors in my laboratory; and my faculty and staff colleagues here at Berkeley.
A Love Affair with Bacillus subtilisMy career in science was launched when I was an undergraduate at Princeton University and reinforced by graduate training at the Massachusetts Institute of Technology. However, it was only after I moved to Harvard University as a junior fellow that my affections were captured by a seemingly mundane soil bacterium. What Bacillus subtilis offered was endless fascinating biological problems (alternative sigma factors, sporulation, swarming, biofilm formation, stochastic cell fate switching) embedded in a uniquely powerful genetic system.
The Unexpected Evolution of Basic Science Studies about Cyclic Nucleotide Action into a Treatment for Erectile DysfunctionIn these Reflections, I describe my perceived role in discoveries made in the cyclic nucleotide field that culminated in the advent of PDE5 inhibitors that treat erectile dysfunction, such as Viagra, Levitra, and Cialis. The discoveries emphasize the critical role of basic science, which often evolves in unpredictable and circuitous paths, in improving human health.
A Passion for ParasitesI knew nothing and had thought nothing about parasites until 1971. In fact, if you had asked me before then, I might have commented that parasites were rather disgusting. I had been at the Johns Hopkins School of Medicine for three years, and I was on the lookout for a new project. In 1971, I came across a paper in the Journal of Molecular Biology by Larry Simpson, a classmate of mine in graduate school. Larry's paper described a remarkable DNA structure known as kinetoplast DNA (kDNA), isolated from a parasite.
The Discovery of Error-prone DNA Polymerase V and Its Unique Regulation by RecA and ATPMy career pathway has taken a circuitous route, beginning with a Ph.D. degree in electrical engineering from The Johns Hopkins University, followed by five postdoctoral years in biology at Hopkins and culminating in a faculty position in biological sciences at the University of Southern California. My startup package in 1973 consisted of $2,500, not to be spent all at once, plus an ancient Packard scintillation counter that had a series of rapidly flashing light bulbs to indicate a radioactive readout in counts/minute.
Wanderings in BiochemistryMy Ph.D. thesis in the laboratory of Severo Ochoa at New York University School of Medicine in 1962 included the determination of the nucleotide compositions of codons specifying amino acids. The experiments were based on the use of random copolyribonucleotides (synthesized by polynucleotide phosphorylase) as messenger RNA in a cell-free protein-synthesizing system. At Yale University, where I joined the faculty, my co-workers and I first studied the mechanisms of protein synthesis. Thereafter, we explored the interferons (IFNs), which were discovered as antiviral defense agents but were revealed to be components of a highly complex multifunctional system.
Life in a Sea of OxygenDuring my third week of high school chemistry, our instructor left in the middle of class in obvious pain and passed away shortly thereafter. This sad event could have spelled disaster for a budding career in chemistry, except for the fact that it occurred at Brandywine High School near Wilmington, Delaware, where 2,500 Ph.D. chemists lived in the school district. These included my father, Robert D. Lipscomb, who, like so many of his DuPont Central Research & Development colleagues, was a product of the Roger Adams/Reynold Fuson/Carl “Speed” Marvel/John Bailar, Jr., era at the University of Illinois.
Master Molecule, Heal ThyselfIn his nearly three decades of leadership in the natural sciences at The Rockefeller Foundation, Warren Weaver contributed substantially to the mid-twentieth century revolution in biology and agricultural science. A veritable polymath, over a lifetime, Weaver also contributed significantly to mathematics, statistics, physics, and computer science and to various scientific associations (1). In the early 1930s, he persuaded Alexander Hollaender, a highly regarded radiobiologist, to survey the literature and write a report for The Rockefeller Foundation on the biological effects of radiation.
The Chemistry of Regulation of Genes and Other ThingsThe truth of a theory lies in the deductive methods used to establish it and the experimental demonstration of its fundamental premises and consequences—Jacques Monod