Helix capping in the GCN4 leucine zipper

Min Lu, Wei Shu, Hong Ji, Erik Spek, Leyu Wang, Neville R. Kallenbach

Research output: Contribution to journalArticlepeer-review


Capping interactions associated with specific sequences at or near the ends of α-helices are important determinants of the stability of protein secondary and tertiary structure. We investigate here the role of the helix-capping motif Ser-X-X-Glu, a sequence that occurs frequently at the N termini of a helices in proteins, on the conformation and stability of the GCN4 leucine zipper. The 1.8 Å resolution crystal structure of the capped molecule reveals distinct conformations, packing geometries and hydrogen-bonding networks at the amino terminus of the two helices in the leucine zipper dimer. The free energy of helix stabilization associated with the hydrogen-bonding and hydrophobic interactions in this capping is -1.2 kcal/mol, evaluated from thermal unfolding experiments. A single cap thus contributes appreciably to stabilizing the terminated helix and thereby the native state. These results suggest that helix capping plays a further role in protein folding, providing a sensitive connector linking α-helix formation to the developing tertiary structure of a protein.

Original languageEnglish (US)
Pages (from-to)743-752
Number of pages10
JournalJournal of Molecular Biology
Issue number4
StatePublished - May 14 1999


  • Coiled coil
  • GCN4 leucine zipper
  • Helix capping
  • Protein folding
  • Thermal stability

ASJC Scopus subject areas

  • Molecular Biology
  • Biophysics
  • Structural Biology


Dive into the research topics of 'Helix capping in the GCN4 leucine zipper'. Together they form a unique fingerprint.

Cite this