PDB Community Focus: Michael G. Rossmann

Michael Rossmann was born in Frankfurt (Main), Germany in 1930. He and his mother moved to England in 1939. He obtained a University of London B.Sc. degree in physics and mathematics. While teaching physics at the Royal Technical College in Glasgow (now the University of Strathclyde), he moonlighted at the University of Glasgow, obtaining a Ph.D. in chemical crystallography under the supervision of John Monteath Robertson. During that time, he married Audrey Pearson. His first two years of postdoctoral studies were in Bill Lipscomb's laboratory at the University of Minnesota where he spent some of his time writing some of the earliest crystallographic computer programs for structure determination and refinement. He returned to England in 1958 to join Max Perutz in Cambridge where he participated in the structure determination of horse oxy-hemoglobin at 5.5 resolution, thereby demonstrating the common evolutionary origin of oxygen carriers, such as hemoglobin and myoglobin. While in Cambridge and inspired by the hemoglobin results, he and David Blow established many of the techniques of modern macromolecular crystallography, including the molecular replacement method.

In 1964, he moved to Purdue University. Initially, he studied dehydrogenases, discovering, in collaboration with Carl Brndn in Sweden and Len Banaszak at Washington University, that these proteins had a common NAD binding fold and, by extrapolation, that there existed a primordial nucleotide binding fold. He initiated his work on virus structure with a 1971 sabbatical half year with Bror Strandberg in Sweden. In 1985, he and his colleagues determined the structure of a common cold virus, the first animal virus to be determined to near atomic resolution, showing that there was a common origin of the capsid protein and assembly for simple RNA animal and plant viruses. This work had required the development of X-ray diffraction data processing techniques and the use of synchrotron methods, including the "American method" (still very much in favor among American politicians) of shooting first and thinking later (i.e. by-passing the old crystallographic technique of first "setting" crystals in order to be able to index the reflections).

He has continued to study numerous viruses, including the West Nile virus, the giant Mimivirus, and the bacteriophage T4. Currently, he is much involved in the use of cryo-electron microscopy (cryoEM) to extend the range of crystallography by combining low resolution cryoEM three-dimensional images with high resolution crystal structures of component proteins.

Q: What was it like working in Cambridge in the 1950s? What made you decide to go to there at this time?

A: Before I went to Cambridge, my interest in crystallography was fueled mainly by an interest in solving the phase problem for specific structures. I had heard a talk by Dorothy Hodgkin at the 1957 IUCr meeting in Montreal on the work in Cambridge by Perutz and Kendrew who were trying to solve the structure of proteins. With thousands of atoms per molecule, this seemed to be the ultimate challenge. Thus, when my postdoctoral time with Bill Lipscomb was nearing its end, I wrote a letter to Max Perutz asking whether he might have a job for me. He replied positively. Later, I discovered that many crystallographers thought that attempting to determine the structure of proteins was an unattainable objective and, hence, Max had had difficulty in finding helpers for his project. No doubt that was why he was now willing to take me into his small group.

Cambridge was a very new experience for me. Max's lab was a part of the famous Cavendish Laboratory where Rutherford, Thompson, and others had laid the foundations of nuclear physics. However, Max's group, initiated under the guidance of Sir Lawrence Bragg before he moved to the Royal Institution in London, had been expelled to a small hut outside the Austin wing of the Cavendish lab. My most important scientific education occurred during the morning coffee breaks when the approximately dozen occupants of the "MRC Hut" met in the crammed entrance area of the hut. This usually included Francis Crick, Sidney Brenner, John Kendrew, and Max. It is here that I began to realize that science is not only about solving puzzles, but, more importantly, recognizing what are the current significant problems susceptible to scientific investigation. We had relatively little contact with University activities, but Max had kindly arranged for me to be a "supervisor" for Peterhouse College. That required meeting with pairs of undergraduates and guiding them in their studies relevant to their current lecture courses. Like most people in England, I had always expected to find the best brains among Cambridge students, but I soon found that even in Cambridge there was quite a spread in ability.

The first year in Cambridge was especially exhilarating. This was the year that we determined the 5.5 structure of hemoglobin and recognized its evolutionary implications. This made an enormous impression on me and has guided my choice of research topics ever since. In the subsequent years, together with David Blow, I explored crystallographic techniques required in the potential determination of other protein structure based on my experience with the hemoglobin structure. It was David who suggested that we should study chymotrypsin together, a project that was subsequently brought to fruition by David and others after I had left Cambridge. These were exciting times, but I have been very fortunate in having experienced many more periods of frantic activity followed by great joy and satisfaction with new discoveries and understanding. Nevertheless, these first true adventures on the frontiers of science made a lasting and deep impression.

Q: You were an early pioneer in methods development for protein crystallography. What drew you to this topic?

A: To some extent, this question has been answered above. I gradually realized that the fun of solving crystallographic puzzles was merely a path to major discoveries in biology and medicine. The significance of the hemoglobin structure, recognized subsequently by a Nobel Prize to Max and John Kendrew, gave great satisfaction. Clearly, the daily fun of writing new computer programs and trying to solve the little daily problems, such as how to scale data on different films, was a fairly certain path to discoveries of major importance.

Q: You have always taken a strong interest in the PDB - why?

A: During the important biological structure meeting at Cold Spring Harbor in 1971, Max called a meeting of all those who had coordinates of a protein structure. This included Fred Richards (ribonuclease), David Phillips (lysozyme), Jan Drenth (papain), and myself (lactate dehydrogenase). Max was concerned about the easy availability and preservation of coordinates. Walter Hamilton, of the Brookhaven National Lab, volunteered to be the curator, thus marking the beginning of the PDB. Sometime later, Fred Richards formed a steering committee that included me.

Although there were less than about a dozen structures in the early 70s, there was a tendency not to release coordinates except to friends. When Martha Ludwig and I were assistant editors to the Journal of Biological Chemistry (JBC), we instituted a policy that if a paper was dependent on a new set of coordinates, then these had to be deposited with the PDB. JBC was probably the first journal that had this policy. However, there were still quite a few published structures whose coordinates were unavailable in the PDB. Spurred on by need, I wrote a program that extracted coordinates from published stereo diagrams (Rossmann, M. G., P. Argos. 1980. Three-dimensional coordinates from stereodiagrams of molecular structures. Acta Crystallogr. B36:819-823). Fortunately, in those days, structural diagrams were usually merely a set of atomic positions joined by bonds. Ribbon diagrams had not yet become popular, although my wife had produced the first such figures based on models of carbonic anhydrase made by Anders Liljas and Bror Strandberg while we were on sabbatical leave in Uppsala (Liljas, A. et al. 1972. Crystal structure of human carbonic anhydrase C. Nat. New Biol. 235:131-137). At the 1976 Erice meeting, I made a plea for the compulsory deposition of coordinates for any published structure.

In more recent years, I have been concerned about maintaining funding and continuity of services by the PDB.

Q: You have used crystallography to study structures ranging from small molecules to proteins to large viruses. Recently, you have been studying structures using cryo-electron microscopy. What do you see as the next challenge?

A: For the PDB, there is a challenge for appropriate archiving of data derived from an increasing variety of physical techniques, including not only the final inferred coordinates, but also the raw data.

More generally, I see trends to look at structures of ever-increasing complexity to a point where the structures of equivalent objects are no longer sufficiently similar to permit crystallization or averaging of single particles observed by electron microscopy. Such problems may require using single particle diffraction techniques, high intensity synchrotron X-ray sources, and tomographic electron microscopic imaging. I expect that we will soon be looking at frozen vitrified single cells and, in the distant future, even observing living cells at near atomic resolution.

Clearly, such work will require ever larger PDB resources to make the results generally available and to avoid loss of information. I see the task of the PDB as being ever more challenging and more essential to all of science. I am seriously afraid of bureaucratic interference in the smooth development and growth of the PDB, which might have major negative impact on scientific progress.

Q: What would be your advice to someone just starting out in structural biology?

A: Keep working in the lab. Enjoy your successes and share them with all who want to know. Find a mentor who can teach you a fundamental appreciation of science like I had the opportunity to learn in Cambridge. Never hide your ignorance, because then nobody can teach you. If you are not enjoying your studies, go and do something else.