Professor Mike Williamson
Head of Department
Tel: 0114 222 4224
My laboratory uses NMR (and other methods where appropriate) to determine the structure and dynamics of proteins in solution and to study their interactions with ligands. In addition we are developing new methods for characterising structures. Further details are in my web page, linked on the top right, and in the publications list. Recent work includes:
We continue to study protein structures, particularly if this illustrates function. Recent targets include the PLAT domain of human polycystin-1, which we show to recognise phosphatidyl serine and PI4P in the membrane; the protein Mms6, which helps assemble magnetite particles in magnetotactic bacteria; and the Wbl protein (Figure), which uses an Fe-S cluster to sense NO in M. tuberculosis and hence evade host defences.
We have studied how proteins recognize polysaccharides such as starch, cellulose, xylan and peptidoglycan in bacterial cell walls: for example, the LysM module which recognises peptidoglycan and chitin, as found in bacterial and fungal cell walls and invertebrate exoskeletons.
We have been developing new tools; in particular the use of high hydrostatic pressure to stabilise partially unfolded structures, and thus investigate functional conformational change in proteins. We have started looking at Rheo-NMR, to see how proteins align and aggregate in laminar flow.
We collaborate with numerous groups. These include a logstanding collaboration with Tetsuo Asakura on silk structure; a collaboration with Jim Thomas on ruthenium-based complexes that bind B-DNA and quadruplexes; a collaboration with Robert Poole on the so-called Carbon Monoxide Releasing Molecules (CORMs); and a study on how Hofmeister ions stabilise and/or solubilise proteins.
We have a longstanding interest in polyphenols such as those from tea, and in how they interact with the body. As part of this study, we have shown that the main component of green tea, epigallocatechin gallate (EGCG), has the potential to slow down HIV infection; and that EGCG can be transported effectively by binding to albumin in the blood.
NMR spectroscopy, structural biology, biochemistry
MBB405 Advanced Research Topics
MBB301 Dynamic proteins - motor proteins and their tracks (Module Coordinator)
MBB266 Biostructures, Energetics and Synthesis
Honours and Distinctions
Mike Williamson's personal page
This page contains a more detailed summary of my research and interests than my main home page.
1975-1978 Natural Sciences, Clare College, Cambridge University (I)
1995 Fellow of the Royal Society of Chemistry and chartered chemist
My research concentrates on protein structure and function, mainly by means of NMR, and is described in more detail below.
I also teach NMR and protein structure, signalling, membranes and molecular motors, as well as numerical and statistical methods. I was a reviewer for the HEFCE QAA Molecular Biosciences reviews in 1998-2000, and coincidentally led the MBB submission, in which we got 24/24. I also headed up the departmental Independent Evaluation of Teaching in 2008, which was also highly complimentary of our teaching. I have been involved in a number of University committees, mostly on admissions, finance and personnel.
I was (2009-2011) Chair of the UK NMR discussion group; also (2009-2012) Chair of the Biochemical Society theme panel II (Molecular structure and function); (2009-2013) a member of BBSRC Committee D (Molecules, Cells and Industrial Biotechnology); and (2005-2009) secretary of Euromar.
I was on sabbatical in Osaka, Japan from September 2008 until September 2009, mainly to write a book, entitled How Proteins Work, published by Garland Press in July 2011 and available online and in all good bookshops. Also available in Italian and Japanese translations.
During my PhD I used NMR to look at the structure and interactions of antibiotics mainly related to vancomycin, still a vital drug in the constant battle against bacterial drug resistance. This led to an interest in the NOE, where I worked first on 1D NOEs, showing that by using a viscous solvent you can make small molecules behave like bigger ones, and determined the definitive structure of vancomycin.
Since then, I have worked both on NMR methodology and on determination of protein structures by NMR. In methodology, I have worked in four main areas:
I have worked on a number of protein systems:
These are protein modules that are used to attach degradative enzymes to their substrate, such as starch, cellulose, xylan and other cell-wall constituents, and also used by bacteria to modify their own or other bacterial cell walls. Our main interest has been in how they recognise specifically their targets, which are chemically very similar: it turns out to be mainly steric rather than using hydrogen bonding. The work has mainly been structural, though we have also worried about enthalpy and entropy, and even a bit of enzymology.
Salivary proline-rich proteins (PRPs) are the major proteins in parotid saliva. A major function appears to be to bind to plant polyphenols (tannins), which we consume in tea, coffee, wine and many fruits and cereals and are responsible for the sensation of astringency. They are unstructured proteins, so their binding is quite different from the more specific interactions that we are more used to seeing for proteins. The study has involved NMR as well as a wide range of other biophysical techniques.
The RegAB two-component signalling system
This is a classic bacterial two-component signalling system, in which an external stimulus (in this case oxygen tension) leads to phosphorylation of a membrane-bound kinase, which then phosphorylates an intracellular response regulator. The phosphorylated regulator undergoes a conformational change, binds to DNA and alters transcription. We expressed it in functional form, showed how it works, and how the DNA is recognised.
The structure of silk is surprisingly poorly understood. In a longstanding collaboration with Prof Tetsuo Asakura at the Tokyo University of Agriculture and Technology, we have worked on protein chemical shifts and also on methods for characterising silk structure, by solution state and solid state NMR. In the silk worm gland, silk is present in a form called Silk I; the better known fibrous form is called Silk II.We recently showed that the crystalline form of silk consists of two different packing arrangements in close proximity. The silk work led to a 2012 publication in Angewandte Chemie in which we show that antiparallel polyalanine crystallises in two different forms depending on its length. This is interesting first because it suggests that spider dragline silk may derive some of its remarkable strength from its polycrystalline form, and second because the completely linear strands have a rather different position in the Ramachandran plot compared to most beta strands: they are distinctly to the left of standard beta-sheet conformation. This suggests that (a) it takes very little energy to distort a beta-strand conformation, and (b) the phi/psi combination (particularly phi) looks to be strongly related to the twistedness of the strand.
In 2014/15 we published three significant papers. Two of these (Okushita et al (2014) Macromolecules 47:4308-16 and Asakura et al (2015) Macromolecules 48:28-36) show definitively that although silk II is indeed an antiparallel beta sheet, it has two different packings, both different from the classic model proposed by Pauling in 1955. The third (Asakura et al (2015) Macromolecules 48:2345-2357) is a review of what is now understood about the structures of silk I and silk II, particularly as understood from NMR.
How to draw single nuclear spins
I have taught NMR for many years. One aspect that has always worried me is the standard textbook introduction to NMR, which draws spins either as being up/down (a) or on two cones (b). Both of these are not helpful when you start to think about pulses. A much more useful representation is to draw spins as more or less randomly distributed in space (c). In a magnetic field there is a slight tendency to point upwards, but it is very slight. This representation is equally compatible with the quantum mechanics, but is much more logically consistent. In particular, it makes much more sense of relaxation, because it shows that relaxation of one spin due to the effect of another (ie dipolar relaxation) is effectively a very short on-resonant pulse - it does not cause a 180 degree flip, merely a small change in orientation. Many of these then add up , in the same way that a large number of random walks lead to diffusion. These ideas are explained more fully in Nature Product Comm. 2019 14:1-9.
We have recently started to be interested in the Hofmeister series. This is a rank ordering of anions, which affect protein stability and solubility. Anions at one end (eg sulphate, phosphate) tend to be highly charged, stabilise proteins but make them less soluble, and are often described as kosmotropes. Ions at the other end (eg thiocyanate) have low charge density, have the opposite effect, and are often called chaotropes. There is disagreement over how they work. We [Bye et al ACS Omega 2016 1:669-679] measured protein chemical shifts in the presence of Hofmeister ions and showed that they all bind, in similar places, though weakly; but that the Hofmeister effects are likely to be due to effects of the ions on water. Work is ongoing.
More recently we have started work on the signalling scaffold protein SH2B1, whhich contains large regions of intrinsically unstructured protein.
We have undertaken a variety of NMR-related projects, mostly with local academics. These include
I have also written a number of reviews, including a recent Perspective on automated protein structure calculation, an update on NOEs in molecular biology, a survey of chemical shift perturbation (Progr NMR Spectrosc, 2013) [an ISI 'Highly Cited' paper], and a review on pressure-induced chemical shifts as probes for conformational fluctuations in proteins.
I am a keen musician (when I have the time!). I play jazz string bass and bass guitar, and have played the cello and bass, as a member of various orchestras, and also in quartets etc. for relaxation, though not recently.
List of publications
h-index of 58 (ISI WoS) and 12500 citations, or find me on google scholar, where I have an h-index of 66 and 19000 citations
As of March 2016, I had a pleasingly symmetrical publication profile on ISI Web of Science: 200 papers published or in press, just over 10000 citations (ie an average of 50 citations per paper), and an h-index of 50 (ie 50 papers with at least 50 citations).
First the NOE book referred to above:
And the recent book:
A selection of early papers:
Papers since 2001:
Kozerski L, Mazurek AP, Kawecki R, Bocian W, Krajewski P, Bednarek E, Sitkowski J, Williamson MP, Moir AJ, Hansen PE
Iwadate M, Asakura T, Dubovskii PV, Yamada H, Akasaka K, Williamson MP
Xie H, Bolam DN, Nagy T, Szabo L, Cooper A, Simpson PJ, Lakey JH, Williamson MP, Gilbert HJ
Bolam DN, Xie H, White P, Simpson PJ, Hancock SM, Williamson MP, Gilbert HJ
Leighton MP, Kelly DJ, Williamson MP, Shaw JG
Xie H, Gilbert HJ, Charnock SJ, Davies GJ, Williamson MP, Simpson PJ, Raghothama S, Fontes CM, Dias FM, Ferreira LM, Bolam DN
Raghothama S, Eberhardt RY, Simpson P, Wigelsworth D, White P, Hazlewood GP, Nagy T, Gilbert HJ, Williamson MP
Jamieson SJ, Williamson MP, Abou-Hachem M, Nordberg KE, Simpson PJ
Charlton AJ, Baxter NJ, Khan ML, Moir AJ, Haslam E, Davies AP, Williamson MP
Simpson PJ, Jamieson SJ, Abou-Hachem M, Karlsson EN, Gilbert HJ, Holst O, Williamson MP
Abou-Hachem M, Karlsson EN, Simpson PJ, Linse S, Sellers P, Williamson MP, Jamieson SJ, Gilbert HJ, Bolam DN, Holst O
Potter CA, Ward A, Laguri C, Williamson MP, Henderson PJ, Phillips-Jones MK
Charlton AJ, Haslam E, Williamson MP
Jakeman DL, Ivory AJ, Blackburn GM, Williamson MP
Horsburgh GJ, Atrih A, Williamson MP, Foster SJ.
Refaee M, Tezuka T, Akasaka K, Williamson MP
Pell G, Williamson MP, Walters C, Du H, Gilbert HJ, Bolam DN
Williamson MP, Akasaka K, Refaee M
Laguri C, Phillips-Jones MK, Williamson MP
Nakano E, Williamson MP, Williams NH, Powers HJ
Joebstl E, O'Connell J, Fairclough JP, Williamson MP
Bocian W, Kawecki R, Bednarek E, Sitkowski J, Pietrzyk A, Williamson MP, Hansen PE, Kozerski L
Tunnicliffe RB, Bolam DN, Pell G, Gilbert HJ, Williamson MP
Exley RM, Shaw J, Mowe E, Sun Y-H, West NP, Williamson MP, Botto, M, Smith H, Tang CM
Flint J, Bolam DN, Nurizzo D, Taylor EJ, Williamson MP, Walters C, Davies GJ, Gilbert HJ
Joebstl E, Fairclough JP, Davies AP, Williamson MP
Tunnicliffe RB, Waby JL, Williams RJ, Williamson MP
Leon-Kempis Mdel R, Guccione E, Mulholland F, Williamson MP, Kelly DJ
Potter CA, Jeong EL, Williamson MP, Henderson PJ, Phillips-Jones MK
Joebstl E, Howse JR, Fairclough JP, Williamson MP
Laguri C, Stenzel RA, Donohue TJ, Phillips-Jones MK, Williamson MP
Williamson MP, Suzuki Y, Bourne NT, Asakura T
Williamson MP, McCormick TG, Nance CL, Shearer WT
Tunnicliffe RB, Ratcliffe EC, Hunter CN, Williamson MP
Moody RG, Phillips-Jones MK, Williamson MP
Cicortas Gunnarsson L, Montanier C, Tunnicliffe RB, Williamson MP, Gilbert HJ, Nordberg Karlsson E, Ohlin M
Nagy T, Tunnicliffe RB, Higgins LD, Walters C, Gilbert HJ, Williamson MP
Wilton DJ, Tunnicliffe RB, Kamatari YO, Akasaka K, Williamson MP
Bocian W, Kawecki R, Bednarek E, Sitkowski J, Williamson MP, Hansen PE, Kozerski L
Wilton DJ, Ghosh M, Chary KV, Akasaka K, Williamson MP
Cioffi M, Hunter CA, Packer MJ, Pandya MJ, Williamson MP
Williamson MP, Craven CJ
Nakazawa Y, Suzuki Y, Williamson MP, Saito H, Asakura T
Tomlinson JH, Ullah S, Hansen PE, Williamson MP
Wilton DJ, Kitahara R, Akasaka K, Williamson MP
Suzuki Y, Takahashi R, Shimizu T, Tansho M, Yamauchi K, Williamson MP, Asakura T
Wilton DJ, Kitahara R, Akasaka K, Pandya MJ, Williamson MP
Waywell P, Thomas JA, Williamson MP
Long J, Garner TP, Pandya MJ, Craven CJ, Chen P, Shaw B, Williamson MP, Layfield R, Searle MS
Tomlinson JH, Craven CJ, Williamson MP, Pandya MJ
Waywell P, Gonzalez V, Gill MR, Adams H, Meijer AJHM, Williamson MP, Thomas JA
Giamarchi A, Feng S, Rodat-Despoix L, Xu Y, Bubenshchikova E, Newby LJ, Hao J, Gaudioso C, Crest M, Lupas AN, Honoré, Williamson MP, Obara T, Ong AC, Delmas P
Wilson T, Williamson MP, Thomas JA
Correia MA, Abbott DW, Gloster TM, Fernandes VO, Prates JA, Montanier C, Dumon C, Williamson MP, Tunnicliffe RB, Liu Z, Flint JE, Davies GJ, Henrissat B, Coutinho PM, Fontes CM, Gilbert HJ
Williamson MP, Sutcliffe MJ
Tomlinson JH, Green VL, Baker PJ, Williamson MP
Ratcliffe EC, Tunnicliffe RB, Ng IW, Adams PG, Qian P, Holden-Dye K, Jones MR, Williamson MP, Hunter CN
Ullah S, Ishimoto T, Williamson MP, Hansen PE
Trotter EW, Rolfe MD, Hounslow AM, Craven CJ, Williamson MP, Sanguinetti G, Poole RK, Green J
Tomlinson JH, Williamson MP
Asakura T, Okonogi M, Horiguchi K, Aoki A, Saitô H, Knight DP, Williamson MP
Williamson MP, Potts JR
Moody RG, Williamson MP
Kitazawa S, Kameda T, Yagi-Utsumi M, Sugase K, Baxter NJ, Kato K, Williamson MP, Kitahara R
Kitahara R, Hata K, Li H, Williamson MP, Akasaka K
Williamson MP, Hounslow AM, Ford J, Fowler K, Hebditch M, Hansen PE
Wilson T, Costa PJ, Félix V, Williamson MP, Thomas JA
Kitazawa S, Kameda T, Kumo A, Yagi-Utsumi M, Baxter NJ, Kato K, Williamson MP, Kitahara R
Mesnage S, Dellarole M, Baxter NJ, Rouget JB, Dimitrov JD, Wang N, Fujimoto Y, Hounslow AM, Lacroix-Desmazes S, Fukase K, Foster SJ, Williamson MP
Okushita K, Asano A, Williamson MP, Asakura T
Asakura T, Ohata T, Kametani S, Okushita K, Yazawa K, Nishiyama Y, Nishimura K, Aoki A, Suzuki F, Kaji H, Ulrich AS and Williamson MP
Asakura T, Okushita K and Williamson MP
Xu Y, Ong ACM, Williamson MP and Hounslow AM
Xu Y, Streets AJ, Hounslow AM, Tran U, Jean-Alphonse F, Needham AJ, Vilardaga JP, Wessely O, Williamson MP and Ong ACM
S. Hollingshead, J. Kopečná, D. R. Armstrong, L. Bučinská, P. J. Jackson, G. E. Chen, M. J. Dickman, M. P. Williamson, R. Sobotka and C. N. Hunter
A.E. Rawlings, J. P. Bramble, A. M. Hounslow, M. P. Williamson, A. E. Monnington, D. J. Cooke and S. S. Staniland
Yasid NA, Rolfe MD, Green J, Williamson MP
J. W. Bye, N. J. Baxter, A. M. Hounslow, R. J. Falconer and M. P. Williamson
J.D. Eaton and M.P.Williamson
Blanchet P, Bebin M, Bruet S, Cooper GM, Thompson ML, Duban-Bedu B, Gerard B, Piton A, Suckno S, Deshpande C, Clowes V, Vogt J, Turnpenny P, Williamson MP, Alembik Y; Clinical Sequencing Exploratory Research Study Consortium; Deciphering Developmental Disorders Consortium, Glasgow E, McNeill A.
Heyam A, Coupland CE, Dégut C, Haley RA, Baxter NJ, Jakob L, Aguiar PM, Meister G, Williamson MP, Lagos D, Plevin MJ
N. J. Baxter, T. Zacharchenko, I. L. Barsukov and M. P. Williamson
B. K. Kudhair, A. M. Hounslow, M. D. Rolfe, J. C. Crack, D. M. Hunt, R. S. Buxton, L. J. Smith, N. E. LeBrun, M. P. Williamson and J. Green
Southam HM, Smith TW, Lyon RL, Liao C, Trevitt CR, Middlemiss LA, Cox FL, Chapman JA, El-Khamisy SF, Hippler M, Williamson MP, Henderson PJF, Poole RK
Pandya MJ, Schiffers S, Hounslow AM, Baxter NJ, Williamson MP
Williamson MP, Kitahara R
Fairbanks SD, Robertson CC, Keene FR, Thomas JA, Williamson MP
Smith RE, Salamaga B, Szkuta P, Hajdamowicz N, Prajsnar TK, Bulmer GS, Fontaine T, Kołodziejczyk J, Herry JM, Hounslow AM, Williamson MP, Serror P, Mesnage S
Wakamoto T, Ikeya T, Kitazawa S, Baxter NJ, Williamson MP, Kitahara R
Iwakawa N, Baxter NJ, Wai DCC, Fowler NJ, Morales RAV, Sugase K, Norton RS, Williamson MP
Gonzalez-Delgado LS, Walters-Morgan H, Salamaga B, Robertson AJ, Hounslow AM, Jagielska E, Sabała I, Williamson MP, Lovering AL, Mesnage S
- Decoration of the enterococcal polysaccharide antigen EPA is essential for virulence, cell surface charge and interaction with effectors of the innate immune system. PLOS Pathogens, 15(5). View this article in WRRO
- Structural Investigation into the Threading Intercalation of a Chiral Dinuclear Ruthenium(II) Polypyridyl Complex through a B-DNA Oligonucleotide.. Journal of the American Chemical Society, 141(11), 4644-4652. View this article in WRRO
- A thiol-reactive Ru(II) ion, not CO release, underlies the potent antimicrobial and cytotoxic properties of CO-releasing molecule-3. Redox Biology, 18, 114-123. View this article in WRRO
- Structure of a Wbl protein and implications for NO sensing by M. tuberculosis. Nature Communications, 8(1). View this article in WRRO
- Pressure-Dependent Chemical Shifts in the R3 Domain of Talin Show that It Is Thermodynamically Poised for Binding to Either Vinculin or RIAM. Structure, 25(12), 1856-1866.e2. View this article in WRRO
- Molecular Mechanism for the Hofmeister Effect Derived from NMR and DSC Measurements on Barnase. ACS Omega, 1(4), 669-679. View this article in WRRO
- Homeostasis of metabolites in Escherichia coli on transition from anaerobic to aerobic conditions and the transient secretion of pyruvate. Royal Society Open Science, 3(8), 160187-160187. View this article in WRRO
- The Polycystin-1, Lipoxygenase, and α-Toxin Domain Regulates Polycystin-1 Trafficking. Journal of the American Society of Nephrology, 27(4), 1159-1173.
- Analysis of the Structure of Bombyx mori Silk Fibroin by NMR. Macromolecules, 48(8), 2345-2357.
- Molecular basis for bacterial peptidoglycan recognition by LysM domains.. Nat Commun, 5, 4269. View this article in WRRO
- Structural studies on dinuclear ruthenium(II) complexes that bind diastereoselectively to an antiparallel folded human telomere sequence.. J Med Chem, 56(21), 8674-8683. View this article in WRRO
- Detection of salt bridges to lysines in solution in barnase.. Chem Commun (Camb), 49(84), 9824-9826.
- Using chemical shift perturbation to characterise ligand binding.. Prog Nucl Magn Reson Spectrosc, 73, 1-16.
- Pressure-induced chemical shifts as probes for conformational fluctuations in proteins. Progress in Nuclear Magnetic Resonance Spectroscopy, 71, 35-58.
- Structure and function of a bacterial Fasciclin I Domain Protein elucidates function of related cell adhesion proteins such as TGFBIp and periostin. FEBS Open Bio, 3, 71-77. View this article in WRRO
- Two Different Packing Arrangements of Antiparallel Polyalanine. ANGEWANDTE CHEMIE-INTERNATIONAL EDITION, 51(5), 1212-1215.
- Reprogramming of escherichia coli K-12 metabolism during the initial phase of transition from an anaerobic to a micro-aerobic environment. PLoS ONE, 6(9). View this article in WRRO
- Amide temperature coefficients in the protein G B1 domain. Journal of Biomolecular NMR, 1-8.
- Experimental evidence that the membrane-spanning helix of PufX adopts a bent conformation that facilitates dimerisation of the Rhodobacter sphaeroides RC-LH1 complex through N-terminal interactions.. Biochim Biophys Acta, 1807(1), 95-107.
- Structural origins of pH-dependent chemical shifts in the B1 domain of protein G.. Proteins, 78(14), 3000-3016.
- Differentiating quadruplexes: binding preferences of a luminescent dinuclear ruthenium(II) complex with four-stranded DNA structures.. Org Biomol Chem, 8(11), 2617-2621.
- Dimerization of protein G B1 domain at low pH: a conformational switch caused by loss of a single hydrogen bond.. Proteins, 78(7), 1652-1661.
- A polycystin-2 (TRPP2) dimerization domain essential for the function of heteromeric polycystin complexes. EMBO J, 29(7), 1176-1191. View this article in WRRO
- Structure of the complex of [Ru(tpm)(dppz)py](2+) with a B-DNA oligonucleotide - a single-substituent binding switch for a metallo-intercalator.. Chemistry, 16(8), 2407-2417.
- Dimerisation of the UBA Domain of p62 Inhibits Ubiquitin Binding and Regulates NF-kappa B Signalling. J MOL BIOL, 396(1), 178-194.
- Pressure-dependent structure changes in barnase on ligand binding reveal intermediate rate fluctuations.. Biophys J, 97(5), 1482-1490.
- Characterization of salt bridges to lysines in the protein G B1 domain.. J Am Chem Soc, 131(13), 4674-4684. View this article in WRRO
- Structural change in a B-DNA helix with hydrostatic pressure.. Nucleic Acids Res, 36(12), 4032-4037. View this article in WRRO
- Binding of topotecan to a nicked DNA oligomer in solution. CHEM-EUR J, 14(9), 2788-2794.
- Characterization of a double dockerin from the cellulosome of the anaerobic fungus Piromyces equi. J MOL BIOL, 373(3), 612-622.
- The solution structure of the PufX polypeptide from Rhodobacter sphaeroides.. FEBS Lett, 580(30), 6967-6971.
- Epigallocatechin gallate, the main polyphenol in green tea, binds to the T-cell receptor, CD4: Potential for HIV-1 therapy.. J Allergy Clin Immunol, 118(6), 1369-1374.
- Binding of amyloid beta-peptide to ganglioside micelles is dependent on histidine-13.. Biochem J, 397(3), 483-490.
- Polyphenol/peptide binding and precipitation.. J Agric Food Chem, 50(6), 1593-1601.
- Characterization of a cellulosome dockerin domain from the anaerobic fungus Piromyces equi.. Nat Struct Biol, 8(9), 775-778.
- The importance of being proline: the interaction of proline-rich motifs in signaling proteins with their cognate domains. FASEB J, 14(2), 231-241.
- The structure and function of proline-rich regions in proteins.. Biochem J, 297 ( Pt 2), 249-260.
- Rapid-pulsing artifacts in double-quantum-filtered COSY. Journal of Magnetic Resonance (1969), 88(1), 177-185.
- SOLUTION CONFORMATION OF PROTEINASE INHIBITOR-IIA FROM BULL SEMINAL PLASMA BY H-1 NUCLEAR MAGNETIC-RESONANCE AND DISTANCE GEOMETRY. J MOL BIOL, 182(2), 295-315.