Stephen Brian Henry Kent

Research Summary
Stephen Kent set out to understand the chemical basis of enzyme catalysis. In a life-long pursuit of that goal, Kent has developed advanced synthetic chemistries, and used them to elucidate the molecular basis of protein function. His early work gave unique insights into the fundamental physicochemical principles underlying polymer-supported peptide synthesis (solid phase peptide synthesis (SPPS)), and led to the identification and minimization of chronic side reactions then affecting SPPS. The resulting highly optimized methods for the chemical synthesis of peptides were commercialized in partnership with Applied Biosystems and became used throughout the world. Kent applied this highly optimized SPPS to studies of the hepatitis B virus and the human immunodeficiency virus (HIV). This work culminated in the idenitifcation, with Robert Neurath, of the immunodominant B- and T-cell epitiopes of the hepatitis B virus, key information for the development of improved hepatitis B vaccines. The highly optimized SPPS methods were also applied to total chemical synthesis of the HIV-1 protease, and led to the determination (with collaborators) of the original crystal structures of the HIV-1 protease enzyme protein molecule complexed with canonical inhibitors. These HIV-1 protease structural data were made freely available and formed the basis of worldwide programs in structure-based drug design that led to the commercial development and rapid introduction of the highly effective ‘protease inhibitor’ class of AIDS therapeutics. The Kent research group pioneered a radically novel approach to the total synthesis of protein molecules, based on the ‘chemical ligation’ principle: chemoselective condensation in aqueous solution of unprotected peptide segments. This principle is embodied in the novel ‘native chemical ligation’ and ‘kinetically-controlled ligation’ chemistries developed by Kent and his colleagues. Chemical ligation has enabled the routine total chemical synthesis of a wide range of high purity, meticulously characterized protein molecules and the consequent general application of physical and organic chemistries to the world of proteins. In the past few years, the Kent lab has pioneered the use of mirror image protein molecules (‘D-proteins’) to facilitate the determination of the X-ray structures of recalcitrant proteins by racemic and quasi-racemic crystallography. Even more recently, the Kent lab has reported the first efficient route to a total chemical synthesis of human insulin, making use of a unique ester-linked polypeptide as a chemical-surrogate for the proinsulin polypeptide chain found in Nature. Currently, the Kent lab and its collaborators are employing a systematic {chemical protein synthesis plus protein phage display} approach to the development of D-proteins as a novel class of molecules for antagonizing the action of natural protein molecules. Such D-protein antagonists may have significant advantages as human therapeutics.
Keywords
chemistry of enzyme catalysis, chemical protein synthesis, chemical ligation, native chemical ligation, racemic protein crystallography, mirror image proteins, ester insulin
Education
  • Victoria University of Wellington, New Zealand, B.Sc. Chemistry & Biochemistry 1968
  • Massey University, New Zealand, M.Sc. Chemistry & Biochemistry 1970
  • University of California, Berkeley, Ph.D. Organic Chemistry & Protein NMR 1974
  • Rockefeller University, R.B. Merrifield Lab, Solid Phase Peptide Synthesis 1977
Biosciences Graduate Program Association
Awards & Honors
  • 1994 - Hirschmann National Award in Peptide Chemistry American Chemical Society
  • 2002 - Kaiser Award The Protein Society
  • 2004 - du Vigneaud Award American Peptide Society
  • 2009 - Merrifield Award American Peptide Society
  • 2010 - Akabori Memorial Medal Japanese Peptide Society
  • 2010 - Rudinger Memorial Medal European Peptide Society
  • 2011 - Bader National Award in Bioorganic Chemistry American Chemical Society
  • 2013 - Leach Medal Lorne Conference on Protein Structure & Function
  • 2017 - Prelog Medal ETH Zurich
  • 2018 - Inaugural Scoffone Award Italian Peptide Society
Publications
  1. Kumar M, Mandal K, Blakeley MP, Wymore T, Kent SBH, Louis JM, Das A, Kovalevsky A. Visualizing Tetrahedral Oxyanion Bound in HIV-1 Protease Using Neutrons: Implications for the Catalytic Mechanism and Drug Design. ACS Omega. 2020 May 26; 5(20):11605-11617. View in: PubMed

  2. Fu C, Demir B, Alcantara S, Kumar V, Han F, Kelly HG, Tan X, Yu Y, Xu W, Zhao J, Zhang C, Peng H, Boyer C, Woodruff TM, Kent SJ, Searles DJ, Whittaker AK. Low-Fouling Fluoropolymers for Bioconjugation and In Vivo Tracking. Angew Chem Int Ed Engl. 2020 03 16; 59(12):4729-4735. View in: PubMed

  3. Kent SBH. Novel protein science enabled by total chemical synthesis. Protein Sci. 2019 02; 28(2):313-328. View in: PubMed

  4. Kent SB. Racemic & quasi-racemic protein crystallography enabled by chemical protein synthesis. Curr Opin Chem Biol. 2018 10; 46:1-9. View in: PubMed

  5. Dang B, Chhabra S, Pennington MW, Norton RS, Kent SBH. Reinvestigation of the biological activity of d-allo-ShK protein. J Biol Chem. 2017 07 28; 292(30):12599-12605. View in: PubMed

  6. Dang B, Shen R, Kubota T, Mandal K, Bezanilla F, Roux B, Kent SB. Inversion of the Side-Chain Stereochemistry of Indvidual Thr or Ile Residues in a Protein Molecule: Impact on the Folding, Stability, and Structure of the ShK Toxin. Angew Chem Int Ed Engl. 2017 03 13; 56(12):3324-3328. View in: PubMed

  7. Gates ZP, Baxa MC, Yu W, Riback JA, Li H, Roux B, Kent SB, Sosnick TR. Perplexing cooperative folding and stability of a low-sequence complexity, polyproline 2 protein lacking a hydrophobic core. Proc Natl Acad Sci U S A. 2017 02 28; 114(9):2241-2246. View in: PubMed

  8. Dhayalan B, Mandal K, Rege N, Weiss MA, Eitel SH, Meier T, Schoenleber RO, Kent SB. Scope and Limitations of Fmoc Chemistry SPPS-Based Approaches to the Total Synthesis of Insulin Lispro via Ester Insulin. Chemistry. 2017 Jan 31; 23(7):1709-1716. View in: PubMed

  9. Gates ZP, Dhayalan B, Kent SB. Obviation of hydrogen fluoride in Boc chemistry solid phase peptide synthesis of peptide-athioesters. Chem Commun (Camb). 2016 Nov 29; 52(97):13979-13982. View in: PubMed

  10. Boerema DJ, Tereshko VA, Zhang J, Kent SB. Chemical synthesis and enzymatic properties of RNase A analogues designed to enhance second-step catalytic activity. Org Biomol Chem. 2016 Sep 21; 14(37):8804-8814. View in: PubMed

  11. Dang B, Kubota T, Mandal K, Correa AM, Bezanilla F, Kent SB. Elucidation of the Covalent and Tertiary Structures of Biologically Active Ts3 Toxin. Angew Chem Int Ed Engl. 2016 07 18; 55(30):8639-42. View in: PubMed

  12. Uppalapati M, Lee DJ, Mandal K, Li H, Miranda LP, Lowitz J, Kenney J, Adams JJ, Ault-Riché D, Kent SB, Sidhu SS. A Potent d-Protein Antagonist of VEGF-A is Nonimmunogenic, Metabolically Stable, and Longer-Circulating in Vivo. ACS Chem Biol. 2016 Apr 15; 11(4):1058-65. View in: PubMed

  13. Dhayalan B, Fitzpatrick A, Mandal K, Whittaker J, Weiss MA, Tokmakoff A, Kent SB. Efficient Total Chemical Synthesis of (13) C=(18) O Isotopomers of Human Insulin for Isotope-Edited FTIR. Chembiochem. 2016 Mar 02; 17(5):415-20. View in: PubMed

  14. Mandal K, Dhayalan B, Avital-Shmilovici M, Tokmakoff A, Kent SB. Crystallization of Enantiomerically Pure Proteins from Quasi-Racemic Mixtures: Structure Determination by X-Ray Diffraction of Isotope-Labeled Ester Insulin and Human Insulin. Chembiochem. 2016 Mar 02; 17(5):421-5. View in: PubMed

  15. Dang B, Dhayalan B, Kent SB. Enhanced Solvation of Peptides Attached to "Solid-Phase" Resins: Straightforward Syntheses of the Elastin Sequence Pro-Gly-Val-Gly-Val-Pro-Gly-Val-Gly-Val. Org Lett. 2015 Jul 17; 17(14):3521-3. View in: PubMed

  16. Bunker RD, Mandal K, Bashiri G, Chaston JJ, Pentelute BL, Lott JS, Kent SB, Baker EN. A functional role of Rv1738 in Mycobacterium tuberculosis persistence suggested by racemic protein crystallography. Proc Natl Acad Sci U S A. 2015 Apr 07; 112(14):4310-5. View in: PubMed

  17. Kent SB. The critical role of peptide chemistry in the life sciences. J Pept Sci. 2015 Mar; 21(3):136-8. View in: PubMed

  18. Kent SB, Alewood PF. Editorial overview: synthetic biomolecules. Curr Opin Chem Biol. 2014 Oct; 22:viii-xi. View in: PubMed

  19. Dang B, Kubota T, Correa AM, Bezanilla F, Kent SB. Total chemical synthesis of biologically active fluorescent dye-labeled Ts1 toxin. Angew Chem Int Ed Engl. 2014 Aug 18; 53(34):8970-4. View in: PubMed

  20. Okamoto R, Mandal K, Sawaya MR, Kajihara Y, Yeates TO, Kent SB. (Quasi-)racemic X-ray structures of glycosylated and non-glycosylated forms of the chemokine Ser-CCL1 prepared by total chemical synthesis. Angew Chem Int Ed Engl. 2014 May 12; 53(20):5194-8. View in: PubMed

  21. Okamoto R, Mandal K, Ling M, Luster AD, Kajihara Y, Kent SB. Total chemical synthesis and biological activities of glycosylated and non-glycosylated forms of the chemokines CCL1 and Ser-CCL1. Angew Chem Int Ed Engl. 2014 May 12; 53(20):5188-93. View in: PubMed

  22. Kent SB. Bringing the science of proteins into the realm of organic chemistry: total chemical synthesis of SEP (synthetic erythropoiesis protein). Angew Chem Int Ed Engl. 2013 Nov 11; 52(46):11988-96. View in: PubMed

  23. Dang B, Kubota T, Mandal K, Bezanilla F, Kent SB. Native chemical ligation at Asx-Cys, Glx-Cys: chemical synthesis and high-resolution X-ray structure of ShK toxin by racemic protein crystallography. J Am Chem Soc. 2013 Aug 14; 135(32):11911-9. View in: PubMed

  24. Avital-Shmilovici M, Mandal K, Gates ZP, Phillips NB, Weiss MA, Kent SB. Fully convergent chemical synthesis of ester insulin: determination of the high resolution X-ray structure by racemic protein crystallography. J Am Chem Soc. 2013 Feb 27; 135(8):3173-85. View in: PubMed

  25. Gates ZP, Stephan JR, Lee DJ, Kent SB. Rapid formal hydrolysis of peptide-athioesters. Chem Commun (Camb). 2013 Jan 28; 49(8):786-8. View in: PubMed

  26. Mandal K, Uppalapati M, Ault-Riché D, Kenney J, Lowitz J, Sidhu SS, Kent SB. Chemical synthesis and X-ray structure of a heterochiral {D-protein antagonist plus vascular endothelial growth factor} protein complex by racemic crystallography. Proc Natl Acad Sci U S A. 2012 Sep 11; 109(37):14779-84. View in: PubMed

  27. Torbeev VY, Kent SB. Ionization state of the catalytic dyad Asp25/25' in the HIV-1 protease: NMR studies of site-specifically 13C labelled HIV-1 protease prepared by total chemical synthesis. Org Biomol Chem. 2012 Aug 14; 10(30):5887-91. View in: PubMed

  28. Yeates TO, Kent SB. Racemic protein crystallography. Annu Rev Biophys. 2012; 41:41-61. View in: PubMed

  29. Mandal K, Pentelute BL, Bang D, Gates ZP, Torbeev VY, Kent SB. Design, total chemical synthesis, and X-ray structure of a protein having a novel linear-loop polypeptide chain topology. Angew Chem Int Ed Engl. 2012 Feb 06; 51(6):1481-6. View in: PubMed

  30. Liu S, Pentelute BL, Kent SB. Convergent chemical synthesis of [lysine(24,38,83)] human erythropoietin. Angew Chem Int Ed Engl. 2012 Jan 23; 51(4):993-9. View in: PubMed

  31. Torbeev VY, Raghuraman H, Hamelberg D, Tonelli M, Westler WM, Perozo E, Kent SB. Protein conformational dynamics in the mechanism of HIV-1 protease catalysis. Proc Natl Acad Sci U S A. 2011 Dec 27; 108(52):20982-7. View in: PubMed

  32. Mandal K, Kent SB. Total chemical synthesis of biologically active vascular endothelial growth factor. Angew Chem Int Ed Engl. 2011 Aug 22; 50(35):8029-33. View in: PubMed

  33. Pollock SB, Kent SB. An investigation into the origin of the dramatically reduced reactivity of peptide-prolyl-thioesters in native chemical ligation. Chem Commun (Camb). 2011 Feb 28; 47(8):2342-4. View in: PubMed

  34. Sohma Y, Hua QX, Whittaker J, Weiss MA, Kent SB. Design and folding of [GluA4(ObetaThrB30)]insulin ("ester insulin"): a minimal proinsulin surrogate that can be chemically converted into human insulin. Angew Chem Int Ed Engl. 2010 Jul 26; 49(32):5489-93. View in: PubMed

  35. Lee DJ, Mandal K, Harris PW, Brimble MA, Kent SB. A one-pot approach to neoglycopeptides using orthogonal native chemical ligation and click chemistry. Org Lett. 2009 Nov 19; 11(22):5270-3. View in: PubMed

  36. Kent SB. Total chemical synthesis of proteins. Chem Soc Rev. 2009 Feb; 38(2):338-51. View in: PubMed

  37. Kent SBH. Novel protein science enabled by total chemical synthesis. Protein Science. 2019; 28:313–328.::::