Irwin Rose (1926-2015).

On June 2, 2015, Irwin (Ernie) Rose died quietly in his sleep at age 88, after a long and fruitful lifetime of sleuthing for the secrets of life at the molecular level. Truly great scientists are much more than the sum of their publications and awards. This is especially true for Ernie who, when informed that he had been awarded the 2004 Nobel Prize in Chemistry, wondered aloud whether he really needed to go to Sweden to receive this honor. Although he did attend the ceremonies, and appeared to enjoy the process enormously, Ernie’s eye was always on the biggest prize of all: understanding how Nature works. Ernie was born in Brooklyn, New York but relocated with his family to Spokane, Washington when he was 13 years old. This move was dictated by the poor health of one of his brothers and the recommendation of a high, dry climate to speed his recovery. Ernie proceeded to make his way through the Spokane public school system and later Washington State University. Although his family was unable to provide him much guidance regarding a research career in biomedical science, this seems not to have deterred him at all. Ernie’s first major research success came as a graduate student at the University of Chicago, where he used the newly available C-14 radioisotope to show that deoxycytidine is produced from its ribonucleoside precursor, cytidine. This important finding immediately implicated a new family of enzymes, the ribonucleotide reductases, in DNA synthesis. Given the degree of chemical and structural detail that Ernie would eventually bring to his research, it is remarkable that this early work was initiated before a 3D structure was available for either DNA or proteins. The ensuing mystery of how enzymes function, a “black box” in the 1950s, was to become a primary focus of Ernie’s laser sharp intellect. Ernie was my teacher. I first met him in 1968, when I joined his laboratory as a postdoctoral researcher. Ernie had become a member of the research staff at the Institute of Cancer Research (ICR) in Fox Chase, Philadelphia, five years earlier, and I was told “how very lucky I was to be able to work with him.” Despite its name, the ICR was led by a forward-looking leader, Timothy Talbot, who recognized that success in biomedical research, cancer included, was ultimately dependent on the vigor of the underlying basic research. By the time I arrived at the ICR, a critical mass of fine researchers had been hired to pursue, among other things, enzyme structure and function. By 1970, the ICR was recognized as a magnet and training ground for anyone interested in this burgeoning research area. Ernie’s contributions to enzyme mechanisms represent some of his proudest accomplishments. His approach was straightforward and deceptively simple, especially in retrospect: How can one prove that enzymes use amino acid side chains to perform acid base chemistry? What is the origin of enzyme stereochemistry and its relationship to catalysis? How do enzymes “reset” themselves after each catalytic turnover? How can cryptic intermediates during enzyme turnover be detected and characterized? The nature of his solutions was anything but simple. For example, Ernie’s demonstration of a role for an active site base in proton removal from an organic substrate came from the detection of an enzymes’ ability to retain and transfer an atom of tritium from an initially labeled position in substrate to a different position in product. His pursuit of enzyme stereochemistry would reveal consistent patterns that could be directly related both to an evolutionary conservation of active site architecture and to a reaction mechanism. The detection of productive intermediates during enzyme turnover, an ongoing and difficult challenge, led to one of Ernie’s most elegant contributions: that of positional isotope exchange (PIX). PIX, generally applicable to ATP-dependent reactions, involves labeling of ATP with O-18 in a bridge position and then monitoring the movement of the labeled oxygen to a nonbridged position within the unreacted pool of starting material. PIX introduced a completely nonperturbative probe for the reversibility of ATP hydrolysis at enzyme active sites, with relevance to many of the most complex enzyme machines found in biology. In the course of his career, Ernie pursued many research interests that extended to the control of glycolysis and the role of ATP in cellular protein breakdown. The latter would ultimately lead to his Nobel Prize, demonstrating—at the molecular level—how proteins become tagged by ubiquitin as the signal for protein arrival at the proteasome and subsequent hydrolysis to small peptides. This discovery emerged from a fortuitous confluence of Ernie’s longstanding interest in protein breakdown and a chance meeting with Avram Hershko, from Technion University, at a Fogerty Conference in Bethesda, Maryland. By 1977 Hershko and his student, Ciechanover, had uncovered a cellular factor in protein degradation (initially referred to as ATP-dependent proteolysis factor, APF-1). Annual visits to the ICR each summer by Hershko led to the mechanism of how APF-1 (renamed ubiquitin) undergoes enzymatic activation to become covalently attached to amino side chains within the protein targeted for degradation. The level of chemical intuition and sophistication that went into the unraveling of this complicated process is beautifully captured in a short retrospective by Ernie, published in 2005 (1). Upon my arrival at the ICR, I immediately felt the “heat” of Ernie’s fierce style of scientific Irwin Rose. Reprinted with permission from University of California, Irvine, CA.