An International Perspective

My studies in chemistry began in 1955 at the University of Sheffield in the United Kingdom. Sheffield was my hometown, but only later in life did I recognize the university’s excellent reputation for chemical and biochemical research. My studies there stimulated a lifelong fascination with biomolecules, how they are produced, their structures, and their modes of action.

In 1961 I began postdoctoral studies with David Sprinson at Columbia University, where every staff member of the biochemistry department was a textbook name. I learned a lot there and loved New York. I became interested in biological electron transfer processes, which were a very hot topic in 1963, and I gained experience in this field through further postdoctoral studies at the universities of Oxford and London. My mentor in London, where I studied the metallo-enzyme xanthine oxidase, was Bob Bray. At the end of my stay in his lab he kindly allowed me to work independently on the nature of copper in pig plasma amine oxidase, recently purified by Hugh Blaschko and Franca Buffoni at Oxford. I collaborated with Buffoni on electron paramagnetic resonance spectroscopy studies that showed that the copper was in the oxidized (cupric) state and remained so following reduction with substrate amine. This surprising observation had also been made by Bruno Mondovi and Helmut Beinert in their studies of pig kidney amine oxidase. The role of copper in the catalytic mechanism of amine oxidases remains controversial to this day.

In 1967 I took a lectureship in the biophysics department at the University of Leeds. My parents were relieved that I had a real job after so many years as a student. I continued work on pig plasma amine oxidase but was interested in other copper enzymes, particularly the cytochrome c oxidase (the membrane-bound enzyme that controls the last step of food oxidation), which seemed to hold the key to understanding oxidative phosphorylation. I knew very little about membranes, and so in 1972 I arranged a short sabbatical to visit the University of Virginia laboratory of Ching Hsien Huang. We had met when we were both postdocs with Manfred Eigen at the Göttingen Max Planck-Institut. During this visit several of us left from Charlottesville and drove up to Meriden, New Hampshire, to attend the Lipid Metabolism Gordon Conference, which was focused specifically on membranes that year. This experience, and my visit with Huang, gave me the confidence to start experiments with model membrane systems. These experiments have continued throughout my career and led to recent work on peptide self-assembly and bio-nanotechnology.

During the 1970s and 1980s my lab focused on analyzing the structure and catalytic mechanisms of amine oxidases using magnetic resonance and kinetic methods. After six years of detailed detective work we had established that the copper centers had two coordinated water molecules, both of which were important to catalytic function. Progress in those days was slow. To understand more about the structure of these proteins, we turned to protein crystallography. Since amine oxidases were big (180,000 daltons), we started with a smaller, related enzyme, galactose oxidase, whose beautiful structure we reported in 1991. In 1995 we reported the first structure of an amine oxidase, which has provided a sound foundation for continued work on the molecular basis of catalysis.

In the 1970s there was a growing awareness that the organic cofactor of amine oxidase was not pyridoxal phosphate but rather was a redox cofactor. The field was greatly stimulated in 1984 when it was reported that the cofactor was a quinine–pyrroloquinoline quinone (PQQ)–that had earlier been found as a dissociable cofactor in bacterial dehydrogenases. Further studies, particularly by Judith Klinman, revealed that the quinone cofactor (TPQ) was the quinone form of trihydroxyphenylalanine derived by redox modification of an active site tyrosine.

By 1990 a substantial population of researchers around the world was interested in quinone cofactors, and Paul Gallop and Herb Kagan organized a GRC called Quinoproteins and Pyrroloquinoline Quinone (PQQ). I returned to the Gordon Conferences after nearly twenty years.

It soon became evident that quinone cofactors like TPQ are only one type of protein modification. We now recognize a large family of enzymes with protein-derived radical cofactors as well as novel cross-links: galactose oxidase is an example with its cysteine-tyrosine cross-link and tyrosine radical cofactor. The title of this GRC has since evolved to encompass radical enzymes involved in rearrangement reactions as well as redox reactions: it is now called Protein-Derived Cofactors, Radicals, and Quinones. Study of these enzymes spans theoretical physics to medicine and involves physicists, chemists, and biological scientists.

My life has been enriched by the friendships I have built over the years attending the Protein-Derived Cofactors series and other Gordon Conferences. Even though we have all been driven by the rivalry of frontier science, we have completely trusted each other with regard to unpublished data. After chairing the Protein-Derived Cofactors Conference in 1997, I was nominated to the GRC board of trustees in 2000, in part, I believe, because I had perspective about the GRC from outside the United States. It has been wonderful to watch the GRC expand from New England to California and Europe, without financial loss and without losing sight of fundamental GRC-brand principles.

I am particularly excited by a new venture to establish GRC sites in developing countries, possibly starting with India. My own research lab has benefited from visiting Indian scientists–in particular, Kapil Yadav from the University of Gorakhpur, who while visiting in the 1980s and 1990s produced the first crystals of galactose oxidase and an amine oxidase, breakthroughs that were crucial to solving the structures of these enzymes. As Shobo Bhattacharya, the director of the Tata Institute for Fundamental Research in Bombay, said in a recent New Scientist article, India needs to present its best science in a context of the frontiers of world science, as should other developing countries. GRC offers the ideal framework for doing this by giving young scientists from around the world a chance to experience the stimulation of Gordon Conferences firsthand.