Serendipitous Alkylation of a Plk1 Ligand Uncovers a New Binding Channel

Nat Chem Biol. 2011 Jul 17;7(9):595-601. doi: 10.1038/nchembio.614.


We obtained unanticipated synthetic byproducts from alkylation of the δ(1) nitrogen (N3) of the histidine imidazole ring of the polo-like kinase-1 (Plk1) polo-box domain (PBD)-binding peptide PLHSpT. For the highest-affinity byproduct, bearing a C(6)H(5)(CH(2))(8)- group, a Plk1 PBD cocrystal structure revealed a new binding channel that had previously been occluded. An N-terminal PEGylated version of this peptide containing a hydrolytically stable phosphothreonyl residue (pT) bound the Plk1 PBD with affinity equal to that of the non-PEGylated parent but showed markedly less interaction with the PBDs of the two closely related proteins Plk2 and Plk3. Treatment of cultured cells with this PEGylated peptide resulted in delocalization of Plk1 from centrosomes and kinetochores and in chromosome misalignment that effectively induced mitotic block and apoptotic cell death. This work provides insights that might advance efforts to develop Plk1 PBD-binding inhibitors as potential Plk1-specific anticancer agents.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alkylation
  • Antineoplastic Agents / chemistry*
  • Antineoplastic Agents / pharmacology
  • Apoptosis / drug effects
  • Binding Sites
  • Cell Cycle Proteins / chemistry*
  • Centrosome / drug effects
  • HeLa Cells
  • Histidine / chemistry*
  • Humans
  • Kinetochores / drug effects
  • Peptides / chemistry
  • Peptides / pharmacology
  • Phosphothreonine / chemistry
  • Polyethylene Glycols / chemistry
  • Protein Binding / drug effects
  • Protein Structure, Tertiary / drug effects
  • Protein-Serine-Threonine Kinases / chemistry*
  • Proto-Oncogene Proteins / chemistry*


  • Antineoplastic Agents
  • Cell Cycle Proteins
  • Peptides
  • Proto-Oncogene Proteins
  • Phosphothreonine
  • Polyethylene Glycols
  • Histidine
  • PLK3 protein, human
  • PLK2 protein, human
  • Protein-Serine-Threonine Kinases
  • polo-like kinase 1

Associated data

  • PDB/3RQ7