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Work on the structure of tRNA


TMV: the direction of assembly
Aaron Klug Scientist
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Then the question about the other 1,000 bases, how do they get covered, they probably get covered by A protein. But then there was a lot of work about discussion about direction, I think you did some experiments with Joe Butler on this didn't you, to find the direction of assembly on the RNA; I've forgotten how you did that.

[Q] We could recognise the ends, I think.

Oh, the ends of it, yes, there's a slight difference in the ends, the tilt of the protein. So... so that system... so it means it's really... it has a biological role, so... so it was some biology entered into a specific recognition, which is what's required. So this is corrected... so it wasn't just a protein cell schlurping in some RNA. So I was very pleased with that and it still remains the best worked out system in viral assembly, as far as I know; where they have been worked out in detail. It was a simple system, the helix is simple to work with as is seen from the spherical virus, this was the... the very best system. So those papers were published in 1971 and I don't know of any other case, although I've stopped looking, I must say now, where this was worked out. And to this day I don't think it's clear how this spherical virus... its recognition probably is part of the RNA. I can imagine it's the same thing, part of the RNA will be some kind of loop structure which is recognised by some partial aggregate, a ring of six or a ring of five sub units of the icosohedral lattice. I thought at one time we would... work on that but one had... by that time we were moving onto other subjects, so...

[Q] The crystals, the fact that we had crystals and the X-ray work progressed on those.

Yes... of course... oh yes... but, now with the crystal, the disc... the disc had a molecular weight of 600,000.

[Q] Yes.

It was the largest object ever, at the time, to be crystallised and solved. It was the first... and to do that; it was a heroic effort, Ann Bloomer, using Uli Arndt's X-ray data collection system that is using a rotating, what was it called?

[Q] Rotation camera.

Rotation camera, and it was solved in 1978 to high resolution. So 76 to five angstroms and to 78 in... low... high resolution.

[Q] Yeah... Yes.

The disc, so that was... but... that... but, you see, being a low resolution, it explained how the hairpin entered the... so the idea was that the hairpin entered through the hole down the middle, a hole in the middle. This loop was recognised by the jaws, there would be two layers with the disc structure. And helix entered, RNA helix and then some other, the dislocator, I can't do that. And the loop was recognised, the guanine's in the loop were recognised.

[Q] Could you see the advantage why it's so far along?

No, we can't, I can't see the advantage. It must be... people have found the origin certainly of some other helical viruses and they are all some distance away. But this... this was met with a lot of suspicion until the Strasbourg people, that is... no, of course, other of the virus plant, virus labs jumped into the act. And a man called Leon Hirth published a paper to prove that this was the case. And... and it was originally he... they published... referred to our work, and... but they showed that they were doing the assembly into a partial intermediates in the assembly. You could see two, two RNA tails coming out of the partially assembled rod; which was the proof that we had the hairpin structure going in.

[Q] Yeah.

It's quite interesting. I think they were quite peeved that we did this because they were professional virologists. And so a bit interesting on the ethos of science... and in the first days they referred to our papers and gradually they published more papers. Our papers got pushed in and so the assembly mechanism is due to Hirth et al. at least in Strasbourg. But we showed it was very clear from your work, in fact you were labelling the ends, it was rather more cumbersome than it just seemed, the two tails, because we had to spread out the RNA to see the two tails, so it was quite pleasing; but, it was the... solving a problem like that. I... one could have gone on had I been a so to speak, a biophysicist, I would have gone onto spherical viruses and done some assembly things and looked at the intermediate aggregates. But one had to give it up to do something new.

Born in Lithuania, Aaron Klug (1926-2018) was a British chemist and biophysicist. He was awarded the Nobel Prize in Chemistry in 1982 for developments in electron microscopy and his work on complexes of nucleic acids and proteins. He studied crystallography at the University of Cape Town before moving to England, completing his doctorate in 1953 at Trinity College, Cambridge. In 1981, he was awarded the Louisa Gross Horwitz Prize from Columbia University. His long and influential career led to a knighthood in 1988. He was also elected President of the Royal Society, and served there from 1995-2000.

Listeners: Ken Holmes John Finch

Kenneth Holmes was born in London in 1934 and attended schools in Chiswick. He obtained his BA at St Johns College, Cambridge. He obtained his PhD at Birkbeck College, London working on the structure of tobacco mosaic virus with Rosalind Franklin and Aaron Klug. After a post-doc at Childrens' Hospital, Boston, where he started to work on muscle structure, he joined to the newly opened Laboratory of Molecular Biology in Cambridge where he stayed for six years. He worked with Aaron Klug on virus structure and with Hugh Huxley on muscle. He then moved to Heidelberg to open the Department of Biophysics at the Max Planck Institute for Medical Research where he remained as director until his retirement. During this time he completed the structure of tobacco mosaic virus and solved the structures of a number of protein molecules including the structure of the muscle protein actin and the actin filament. Recently he has worked on the molecular mechanism of muscle contraction. He also initiated the use of synchrotron radiation as a source for X-ray diffraction and founded the EMBL outstation at DESY Hamburg. He was elected to the Royal Society in 1981 and is a member of a number of scientific academies.

John Finch is a retired member of staff of the Medical Research Council Laboratory of Molecular Biology in Cambridge, UK. He began research as a PhD student of Rosalind Franklin's at Birkbeck College, London in 1955 studying the structure of small viruses by x-ray diffraction. He came to Cambridge as part of Aaron Klug's team in 1962 and has continued with the structural study of viruses and other nucleoproteins such as chromatin, using both x-rays and electron microscopy.

Tags: Joe Butler, Ann Bloomer, Uli Arndt, Leon Hirth

Duration: 5 minutes, 2 seconds

Date story recorded: July 2005

Date story went live: 24 January 2008