Invited Speaker International Peptide Symposium 2023

Through the Looking Glass – a new world of proteins enabled by chemistry (#118)

Stephen Kent 1
  1. Department of Chemistry, University of Chicago, Chicago, USA

The ribosomally-translated protein molecules found in Nature are homochiral. They made up of L-amino acids and the achiral amino acid glycine. Modern chemical ligation methods enable the total synthesis of unnatural protein molecules made up entirely of D-amino acids and glycine.[1-3] These D-proteins have a folded structure that is the mirror image of their counterparts found in Nature. The prototypical synthesis of a mirror image enzyme molecule demonstrated reciprocal chiral substrate specificity.[4,5] Mirror image protein molecules have a variety of uses.[6] Crystallization of racemic protein mixtures consisting of D-protein and L-protein enantiomers has greatly facilitated the solution of novel protein X-ray structures.[7,8] Most importantly, D-proteins enable ‘mirror image drug discovery’, to identify unique therapeutic leads from chiral compound libraries.[9] D-Protein molecules themselves are good candidates for use as human therapeutics: they are resistant to proteolytic digestion, are longer-lived in vivo, and are non-immunogenic.[10] To illustrate the properties and applications of mirror image protein molecules, I will describe the application of total synthesis to the creation of uniquely chemical D-protein antagonists of an important therapeutic target.[11]

  1. Constructing proteins by dovetailing unprotected synthetic peptides: backbone engineered HIV protease. M. Schnölzer, S. Kent. Science, 256, 221-225 (1992).
  2. Synthesis of proteins by native chemical ligation. Philip E. Dawson, Tom W. Muir, Ian Clark-Lewis, Stephen B.H. Kent. Science, 266, 776-779 (1994).
  3. Native chemical ligation in protein synthesis and semi-synthesis. Anne C. Conibear, Emma E. Watson, Richard J. Payne, Christian F. W. Becker. Chem. Soc. Rev., 2018, 47, 9046-9068.
  4. Total chemical synthesis of a D-enzyme: the enantiomers of HIV-1 protease demonstrate reciprocal chiral substrate specificity, R.C deLisle Milton, S.C.F. Milton, and S.B.H. Kent, Science, 256, 1445-1448 (1992).
  5. Synthesis of proteins by chemical ligation of unprotected peptide segments: mirror-image enzyme molecules D- & L-HIV protease analogues. R. deLisle Milton, Saskia Milton, Martina Schnölzer, Stephen B.H. Kent, in "Techniques in Protein Chemistry IV", R. Angeletti, ed., Academic Press, New York, 1993, pp. 257-267.
  6. Synthesis and applications of mirror-image proteins. Katriona Harrison, Angus S. Mackay, Lucas Kambanis, Joshua W. C. Maxwell, Richard J. Payne, Nature Reviews Chemistry, 7, 383–404 (2023).
  7. Racemic protein crystallography. Todd O. Yeates, Stephen B.H. Kent. Ann. Review Biophysics, 41, 41–61 (2012).
  8. Chemical synthesis and X-ray structure of a heterochiral {D-protein antagonist plus VEGF-A} protein complex by racemic crystallography. Kalyaneswar Mandal, Maruti Uppalapati, Dana Ault-Riché, John Kenney, Joshua Lowitz, Sachdev Sidhu, Stephen B.H. Kent. Proc Natl Acad Sci USA, 109, 14779-14784 (2012).
  9. Identification of D-peptide ligands through mirror-image phage display. Science, 271, 1854-1857 (1996).
  10. A potent D-protein antagonist of VEGF-A is non-immunogenic, metabolically stable and longer-circulating in vivo. Maruti Uppalapati, Dong Jun Lee, Kalyaneswar Mandal, Hongyan Li, Les P. Miranda, Joshua Lowitz, John Kenney, Jarrett J. Adams, Dana Ault-Riché, Stephen B. H. Kent, Sachdev S. Sidhu, ACS Chemical Biology, 11, 1058-65 (2016).
  11. A designed bivalent D-protein potently inhibits retinal vascularization and tumor growth. Paul S. Marinec, et al., ACS Chemical Biology, 16, 548–556 (2021).