Autobiography Aaron Klug . The Nobel Prize in Chemistry 㰀⼀琀椀琀氀攀㸀
<META http-equiv=Content-Style-Type content=text/css><LINK href="style.css" type=text/css rel=stylesheet><head></head>㰀戀漀搀礀 戀最挀漀氀漀爀㴀最爀愀礀 氀攀昀琀洀愀爀最椀渀㴀㜀 㸀
㰀栀㈀ 愀氀椀最渀㴀挀攀渀琀攀爀㸀
The Nobel Prize in Chemistry 1982 </h2>㰀栀㌀ 愀氀椀最渀㴀挀攀渀琀攀爀㸀䄀愀爀漀渀 䬀氀甀最
</h3><h4>㰀倀㸀一甀挀氀攀椀挀 愀挀椀搀ⴀ瀀爀漀琀攀椀渀 挀漀洀瀀氀攀砀攀猀㰀⼀瀀㸀㰀瀀㸀
</p><p>Understanding the basic machinery of life: protein biosynthesis
Proteins are the &laqno;workhorses» of the living cell: they are used as enzymes to catalyse metabolic reactions, as antibodies to protect higher organisms against pathogens, as structural motors and as signal transducers between the outside of the cell and the nucleus which stores the genetic information.㰀椀洀最 愀氀椀最渀㴀爀椀最栀琀 戀漀爀搀攀爀㴀㈀ 猀爀挀㴀∀⸀最椀昀∀㸀㰀⼀瀀㸀㰀瀀㸀
The way genetic information is specifically translated into proteins depends in part upon specific interactions between nucleic acids and protein molecules. In order to elongate the growing polypeptide chain with the correct amino acid, one important step is the correct attachment of cognate amino acids onto their cognate tRNA molecules, which is catalysed by specific enzymes called tRNA synthetases. Much work has been done at the EMBL in Grenoble by the group headed by S. Cusack to understand the structural basis of these interactions. ID2 has enabled high-resolution structure determination of several aminoacyl-tRNA synthetases and their complexes with cognate tRNA (Table 1). Protein biosynthesis is carried out by numerous enzymes, tRNAs and other protein factors which act in concert with a macromolecular complex called the ribosome, where the synthesis of the growing polypetide actually takes place. This &laqno;factory» consists of many proteins (up to 73) and several RNA molecules which ensure a coordinated translation of the genetic code. Several crystals from different ribosomal systems have been grown and are being characterised by the group of Dr Yonath at Hamburg and at the ESRF on ID2. Together, through obtaining better images of these macromolecular assemblies, this work opens the way to a better understanding of the mechanism and the interactions crucial for the protein biosynthesis machinery.㰀⼀瀀㸀㰀瀀㸀
Large bio-assemblies tend in general to give only tiny crystals with volumes less than 105 mm3, even after years of crystallisation trials. Such crystals diffract very weakly and adequate data cannot be collected using conventional X-ray sources. This has hitherto prevented structure determination of important biological systems like membrane proteins.㰀⼀瀀㸀㰀瀀㸀
Furthermore large macromolecular assemblies yield crystals with large unit cells (some virus crystals have unit-cell parameters up to 1500 Å). These sample peculiarities require both a high photon flux through a small cross-section and also an essentially parallel beam. With such characteristics, the many closely-spaced spots from a large unit-cell crystal can be resolved and a good signal-to-noise for weak reflections can be obtained.㰀⼀瀀㸀㰀瀀㸀
The High Brilliance beamline ID2, with a highly collimated undulator source, ideally fulfils the requirements for crystallography of biological complexes. ID2 provides one of the most brilliant X-ray source for Macromolecular Crystallography in the world and was one of the first ESRF beamlines to become operational in September 1994. The beamline is devoted to macromolecular crystallography experiments for half of the usable time, the other half being devoted to small-angle scattering (including on biological samples such as muscle fibres) on the second end-station. ID2 is equipped with two undulators (46 mm and 26 mm) which produce a small (100 x 100 µm) parallel beam with a flux of about 6 x 1012 ph/s/100 mA through the sample. In addition, two cryocooling devices (Oxford Instruments Cryostream and a coaxial FTS system) allow regulation of the sample temperature between 100 K and 293 K. Data collection at low temperatures, preferably at 100 K if the crystal can be frozen, is essential to avoid radiation damage and obtain more accurate measurements. A five-circle Huber diffractometer with a long 2 arm allows positioning of the detector up to 1m away from the crystal. This allows diffraction spots from crystals with very large unit cells (up to 1500 Å for crystals containing whole viral particles) or large mosaicity (which was the case for the membrane protein Photosystem I) to be resolved. In addition, the 2 arm can also be swung (± 20 degrees) allowing high resolution data to be collected even at long crystal-to-detector distances.㰀⼀瀀㸀㰀瀀㸀
A number of structural biology projects, including complete virus particles, targets for drug-design, membrane proteins and nucleic acid-protein complexes have made use of the beamline (some of them are listed in Table 1). For many systems ID2 has provided the experimenters with data to higher resolution than previously achieved, allowing a more detailed understanding of fundamental biological phenomena, for example viral replication or plant photosynthesis. Of the many demanding projects that were successfully carried out over the past two and a half years of operation, we have selected four examples to illustrate how a high brilliance X-ray source can be utilised to probe and understand large biological assemblies.
</p><p>嘀椀爀甀猀攀猀㬀 䈀氀甀攀 吀漀渀最甀攀 嘀椀爀甀猀㰀⼀瀀㸀㰀瀀㸀
Understanding viruses that infect cattle and how to combat them㰀⼀瀀㸀㰀瀀㸀
Blue Tongue Virus (BTV), an orbivirus, is a member of the Reoviridae family and infects ruminants and domestic cattle, causing diseases of great economic importance. The Blue Tongue Virus project has been described in some detail in the ESRF Highlights 1995/1996. We would like to summarise the overall status of this project. The virus particle is very large in structural terms (800 Å in diameter and with a molecular weight of 60 MDa) and is composed of 4 capsid proteins (with differing copy numbers ranging from 120 to 780) and 10 unique double-strand ribonucleic acids, each associated with its transcription complex (made up of 3 or 4 proteins). Core particles, with the two outer capsid proteins removed, have been crystallised by D. Suart's group at Oxford and diffraction data have been collected at ID2 on several occasions. These data to 3.5 Å resolution could not have been collected at any other beamline. The Blue Tongue Virus project is probably the largest biological assembly giving well-diffracting and interpretable diffraction data and a near atomic resolution structure (3.5 Å).
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HIV1-Reverse-Transcriptase (RT)䤀洀瀀爀漀瘀攀搀 搀爀甀最 搀攀猀椀最渀 琀漀 瀀爀攀瘀攀渀琀 䄀䤀䐀匀㼀
</p><p>吀栀攀 最攀渀漀洀攀 漀昀 䠀䤀嘀 ⠀琀栀攀 挀愀甀猀愀琀椀瘀攀 愀最攀渀琀 漀昀 䄀䤀䐀匀⤀ 攀渀挀漀搀攀猀 琀栀爀攀攀 攀渀稀礀洀攀猀Ⰰ 攀愀挀栀 眀椀琀栀 愀渀 攀猀猀攀渀琀椀愀氀 昀甀渀挀琀椀漀渀 椀渀 琀栀攀 椀渀昀攀挀琀椀漀甀猀 挀礀挀氀攀 漀昀 琀栀攀 瘀椀爀甀猀⸀ 伀渀攀 漀昀 琀栀攀猀攀 攀渀稀礀洀攀猀Ⰰ 琀栀攀 爀攀瘀攀爀猀攀 琀爀愀渀猀挀爀椀瀀琀愀猀攀 漀爀 刀吀Ⰰ 椀猀 爀攀猀瀀漀渀猀椀戀氀攀 昀漀爀 琀栀攀 挀漀渀瘀攀爀猀椀漀渀 ⠀琀爀愀渀猀挀爀椀瀀琀椀漀渀⤀ 漀昀 琀栀攀 瘀椀爀愀氀 最攀渀漀洀攀 椀渀琀漀 䐀一䄀 洀漀氀攀挀甀氀攀猀 眀栀椀挀栀 愀爀攀 琀栀攀渀 椀渀挀漀爀瀀漀爀愀琀攀搀 椀渀琀漀 琀栀攀 栀漀猀琀ⴀ挀攀氀氀 最攀渀漀洀攀⸀ 䄀猀 愀 挀爀甀挀椀愀氀 攀氀攀洀攀渀琀 椀渀 琀栀攀 椀渀昀攀挀琀椀漀甀猀 挀礀挀氀攀Ⰰ 琀栀椀猀 攀渀稀礀洀攀 栀愀猀 戀攀攀渀 琀栀攀 瀀爀椀洀愀爀礀 琀愀爀最攀琀 昀漀爀 愀渀琀椀瘀椀爀愀氀 琀栀攀爀愀瀀礀Ⰰ 愀渀搀 愀渀愀氀漀最甀攀猀 漀昀 琀栀攀 戀甀椀氀搀椀渀最 戀氀漀挀欀猀 漀昀 䐀一䄀 猀甀挀栀 愀猀 䄀娀吀 漀爀 䐀䐀䤀 栀愀瘀攀 戀攀攀渀 甀猀攀搀 愀猀 琀攀渀琀愀琀椀瘀攀 䄀䤀䐀匀 琀栀攀爀愀瀀攀甀琀椀挀 愀最攀渀琀猀 戀攀挀愀甀猀攀 琀栀攀礀 戀椀渀搀 琀漀 刀吀 愀渀搀 瀀爀攀瘀攀渀琀 椀琀猀 昀甀渀挀琀椀漀渀⸀ 匀攀瘀攀爀愀氀 洀甀琀愀琀椀漀渀猀 栀漀眀攀瘀攀爀 栀愀瘀攀 戀攀攀渀 漀戀猀攀爀瘀攀搀 眀椀琀栀椀渀 琀栀攀 刀吀 洀漀氀攀挀甀氀攀Ⰰ 眀栀椀挀栀 攀渀愀戀氀攀 椀琀 琀漀 攀猀挀愀瀀攀 琀栀攀 戀椀渀搀椀渀最 漀昀 琀栀攀猀攀 搀爀甀最猀⸀ 䐀攀琀愀椀氀攀搀 猀琀爀甀挀琀甀爀愀氀 椀渀昀漀爀洀愀琀椀漀渀 漀昀 洀甀琀愀琀攀搀 昀漀爀洀猀 漀昀 琀栀攀 刀吀 洀漀氀攀挀甀氀攀 愀爀攀 渀攀攀搀攀搀 椀渀 漀爀搀攀爀 琀漀 甀渀搀攀爀猀琀愀渀搀 琀栀攀 眀愀礀 琀栀攀猀攀 洀甀琀愀琀椀漀渀猀 愀氀氀漀眀 琀栀攀 刀吀 琀漀 攀猀挀愀瀀攀 戀椀渀搀椀渀最 漀昀 攀砀椀猀琀椀渀最 搀爀甀最猀 愀渀搀 琀漀 栀攀氀瀀 搀攀猀椀最渀 漀琀栀攀爀猀⸀ 匀椀渀挀攀 刀吀 椀猀 愀 氀愀爀最攀 攀渀稀礀洀攀 挀漀渀琀愀椀渀椀渀最 猀攀瘀攀爀愀氀 猀甀戀搀漀洀愀椀渀猀 氀椀渀欀攀搀 戀礀 昀氀攀砀椀戀氀攀 猀攀最洀攀渀琀猀Ⰰ 挀爀礀猀琀愀氀猀 栀愀瘀攀 戀攀攀渀 攀砀琀爀攀洀攀氀礀 搀椀昀昀椀挀甀氀琀 琀漀 瀀爀漀搀甀挀攀 愀渀搀 甀猀甀愀氀氀礀 搀椀昀昀爀愀挀琀 瀀漀漀爀氀礀⸀
</p><p>吀栀攀 琀攀挀栀渀椀挀愀氀 挀栀愀爀愀挀琀攀爀椀猀琀椀挀猀 漀昀 䤀䐀㈀ 栀愀瘀攀 栀攀氀瀀攀搀 琀栀攀 伀砀昀漀爀搀 最爀漀甀瀀 琀漀 挀漀氀氀攀挀琀 栀椀最栀攀爀 爀攀猀漀氀甀琀椀漀渀 搀愀琀愀 漀渀 琀栀攀猀攀 瀀爀漀樀攀挀琀猀 愀渀搀 瀀爀漀搀甀挀攀 愀 挀氀攀愀爀攀爀 甀渀搀攀爀猀琀愀渀搀椀渀最 漀昀 琀栀椀猀 攀渀稀礀洀攀⸀
㰀⼀瀀㸀㰀瀀㸀
䴀攀洀戀爀愀渀攀 瀀爀漀琀攀椀渀猀㬀 瀀栀漀琀漀猀礀猀琀攀洀 䤀
Understanding plant photosynthesis㰀⼀瀀㸀㰀瀀㸀
Photosynthesis is the process whereby solar light energy is converted into a chemical form readily available to living systems. Two groups of plant photosystems (numbered PSI and PSII according to the nature of their terminal electron acceptor: either an iron sulphur cluster or a quinone molecule) have been extensively studied through biochemical, spectroscopic and structural methods. The large chlorophyl antenna of PSI capture and channel excitation energy to the primary electron donors (chlorophyl molecules) located near the light-sensitive side of the membrane, which further transfer the electron to Fe4S4 clusters. On the basis of data collected on ID2 to 3.8 Å resolution, which have been recently extended to 3.5 Å resolution, the geometry of the cofactors, which are important structural elements within the electron transfer chain, could be imaged much more precisely (Figure 1). The fine collimation of the beam provided by ID2 proved to be essential for resolving broad spots due to a large mosaicity of the crystals. This structure determination has provided a basis for understanding photosynthetic reaction centres involving iron sulphur clusters. Furthermore, this result has an interesting implication for understanding the evolution of photosynthetic systems within plants: despite a low level of primary sequence homology (the sequence of amino-acids of the two PS bear no obvious resemblance), structural analogy between PSI and PSII indicates that these two classes of photosynthetic systems may derive from a common ancestral molecule.
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䤀 眀愀猀 戀漀爀渀 椀渀 㤀㈀㘀 琀漀 䰀愀稀愀爀 愀渀搀 䈀攀氀氀愀 ⠀渀攀 匀椀氀椀渀⤀ 䬀氀甀最 椀渀 娀攀氀瘀愀猀Ⰰ 䰀椀琀栀甀愀渀椀愀Ⰰ
but remember nothing of the place, because I was brought to South Africa as a child of two and grew up there. My father was trained as a saddler, but in fact as a young man worked in his father's business of rearing and selling cattle, so he grew up in the countryside. He had a traditional Jewish education and secular schooling, and though not a conventionally well educated man, he had some gift for writing, and had a number of articles published in the newspapers of the capital, for which he acted as what would now be called a stringer. Shortly after I was born he emigrated to Durban, where members of my mother's family had settled at the turn of the century, and the rest of the family followed soon thereafter.㰀瀀㸀
Durban was then a relatively sleepy town in subtropical surroundings. It was a fine place for a boy - there was the beach and the bush and school was not too taxing. I went to a good school, Durban High School, which was run on traditional English lines, with a curriculum somewhat adapted to South African circumstances. We had some good masters particularly in History and English. However, by the standards of to-day, there were few challenges other than Advanced Latin Prose Composition in the 6th Form. The philosophy of the school was quite simple - the bright boys specialised in Latin, the not so bright in science and the rest managed with geography or the like. There was a good library but it was the playing fields that kept one out of mischief. I did not feel a particularly strong call to any one subject, but read voraciously and widely and began to find science interesting. It was the book called Microbe Hunters by Paul de Kruif, well known in its time, which influenced me to begin medicine at university as a way into microbiology.㰀⼀瀀㸀㰀瀀㸀
At the University of Witwatersrand in Johannesburg, I took the pre-medical course and, in my second year, I took, among other subjects, biochemistry, or physiological chemistry as it was then called, which stood me in good stead in later years when I came to face biological material. However, I felt the lack of a deeper foundation, and moved to chemistry and this in turn led me to physics and mathematics. So finally I took a science degree.㰀⼀瀀㸀㰀瀀㸀
I had by then decided that I wanted to do research in physics and I went to the University of Cape Town which was then offering scholarships which enabled one to do an M.Sc. degree, in return for demonstrating in laboratory classes. The University lay in a beautiful site on the slopes of Table Mountain, which one climbed at week-ends. I was lucky to find as Professor there, R.W. James, the X-ray crystallographer, who had brought to Cape Town the traditions of the Bragg school at Manchester. He was an excellent teacher and I used to attend his undergraduate lectures as well as those in the M.Sc. course. From him I acquired a feeling for optics, and a knowledge of Fourier theory, and I remember particularly certain optical experiments on rather abstruse phenomena such as external and internal conical refraction which fascinated me. After taking my M.Sc. degree, I stayed on and worked on the X-ray analysis of some small organic compounds, in the course of which I developed a method of using molecular structure factors for solving crystal structures, and taught myself some quantum chemistry to calculate bond lengths and so on. During this time, I developed a strong interest, broadly speaking, in the structure of matter, and how it was organised. I had now acquired a good knowledge of X-ray diffraction, not only through my own work, but through having helped James check the proofs of his fine book - The Optical Principles of the Diffraction of X-rays - still a standard work. James wrote beautifully and fully and took great pains to make everything clear.㰀⼀瀀㸀㰀瀀㸀
Supported by an 1851 Exhibition Scholarship and also by a research studentship to Trinity College, I went to Cambridge in 1949. Cambridge was the place for someone from the Colonies or the Dominions to go on to, and it was to the Cavendish Laboratory that one went to do physics. I wanted to work on some form of "unorthodox" X-ray crystallography, for example protein structure, but the MRC Unit where Perutz and Kendrew were working was full, and Bragg, then the Cavendish Professor, had closed down a project on order - disorder phenomena in alloys, which interested me. I finally found myself a research student of D.R. Hartree, who had been a colleague of both Bragg and James at Manchester. He suggested to me a theoretical problem left over from his work during the war on the cooling of steel through the austenite-pearlite transition, and I learned a fair amount of metallurgy in order to understand the physical basis of the phenomenon. It turned out however in the end that it was not special crystallographic insight that was called for - the course of the transition was in practice governed by the diffusion of the latent heat and I ended up using numerical methods to solve the partial differential equations for heat flow in the presence of a phase transition. I learned a good deal during this time, particularly in computing and solid state physics, and the idea of nucleation and growth in a phase change had its echo when I came later to think about the assembly of tobacco mosaic virus.㰀⼀瀀㸀㰀瀀㸀
After taking my Ph.D., I spent a year in the Colloid Science department in Cambridge, working with F.J.W. Roughton, who had asked Hartree for someone to help him tackle the problem of simultaneous diffusion and chemical reaction, such as occurs when oxygen enters a red blood cell. The methods I had developed for the problem in steel were applicable here, and I was glad to put them to use on an interesting new problem. The quantitative data came from experiments in which thin layers of blood were exposed to oxygen or carbon monoxide. In the course of my stay there, I also showed how one could analyse the experimental kinetic curves for the reaction of haemoglobin with carbon dioxide or oxygen by simulations in the computer, and so fit the rate constants.㰀⼀瀀㸀㰀瀀㸀
This work made me more and more interested in biological matter, and I decided that I really wanted to work on the X-ray analysis of biological molecules. I obtained a Nuffield Fellowship to work in J.D. Bernal's department in Birkbeck College in London and I moved there at the end of 1953. I joined a project on the protein ribonuclease, but shortly afterwards met Rosalind Franklin, who had moved to Birkbeck earlier and had begun working on tobacco mosaic virus. Her beautiful X-ray photographs fascinated me and I was also able to interpret some pictures which had apparently anomalous curved layer lines in terms of the splitting which occurs when the helical parameters are non-rational. From then on my fate was sealed. I took up the study of tobacco mosaic virus, and in four short years, together with Kenneth Holmes and John Finch, who had joined us as research students, we were able to map out the general outline of the structure of tobacco mosaic virus. This work was done partly in parallel with that of Donald Caspar, then at Yale, but he spent 1955 - 56 in Cambridge, and I formed an association with him which continued across the Atlantic for many years. It was during this time that I met Francis Crick and we published a paper together on diffraction by helical structures. I was fortunate to work with him again later, and so be able to learn, as he once wrote of Bragg, from watching the way he went about a problem.㰀⼀瀀㸀㰀瀀㸀
Rosalind Franklin died in 1958 and, supported by an N.I.H. grant, Finch, Holmes and I continued the work on viruses, now extended to spherical viruses. We were joined soon after by Reuben Leberman, a biochemist. In 1962 we moved to the newly built MRC Laboratory of Molecular Biology in Cambridge which, under the leadership of Perutz, was to house the original unit from the Cavendish Laboratory (Perutz, Kendrew, Crick and, later, Brenner), enlarged by Sanger's group from the Biochemistry Department and Hugh Huxley from University College London. I was thus privileged to join the laboratory at this stage in its expansion and so be able to take advantage of, and to help build up, its unique environment of intellectual and technological sophistication. The rest of my scientific career is largely a matter of record and much of this is dealt with in the lecture that follows.㰀⼀瀀㸀㰀瀀㸀
However, I should perhaps add that during the 20 years I have been back in Cambridge, I have been actively involved in the teaching of undergraduates, as well as of course supervising research students. I am still a Director of Studies in Natural Science at my College, Peterhouse, and under the tutorial or - as it is called in Cambridge - supervision, system, I teach undergraduates myself. I like teaching and the contact with young minds keeps one on one's toes, but increasing responsibilities have forced me to shed much of it in recent years.㰀⼀瀀㸀㰀瀀㸀
Before I came to Cambridge I married Liebe Bobrow whom I had met in Cape Town. She trained in modern dance at the Jooss-Leeder School in London and later became a choreographer and coordinator for the Cambridge Contemporary Dance Group. More recently she has directed and acted in the theatre. We have two sons, Adam and David, born in 1954 and 1963. Adam, after studying History and Economics at Oxford and the London School of Economics, is now doing research in Econometrics. David is a second year student of Physics.㰀⼀瀀㸀㰀瀀㸀
㰀⼀栀㐀㸀
㰀猀琀爀漀渀最㸀猀瀀漀渀猀漀爀猀 氀椀渀欀 㰀愀 栀爀攀昀㴀∀栀琀琀瀀㨀⼀⼀琀甀渀椀渀最 㘀㌀⸀爀甀⼀∀㸀︀ 㰀⼀愀㸀 㰀戀爀㸀 㰀愀 栀爀攀昀㴀∀栀琀琀瀀㨀⼀⼀爀攀最椀漀渀琀攀栀猀渀愀戀⸀爀甀⼀∀㸀︀ 㰀⼀愀㸀㰀⼀猀琀爀漀渀最㸀㰀⼀戀漀搀礀㸀㰀⼀栀琀洀氀㸀