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1ce9
From Proteopedia
HELIX CAPPING IN THE GCN4 LEUCINE ZIPPER
Overview
Capping interactions associated with specific sequences at or near the ends of alpha-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 alpha helices in proteins, on the conformation and stability of the GCN4 leucine zipper. The 1.8 A 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 structure 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 alpha-helix formation to the developing tertiary structure of a protein.
About this Structure
1CE9 is a Single protein structure. Full crystallographic information is available from OCA.
Reference
Helix capping in the GCN4 leucine zipper., Lu M, Shu W, Ji H, Spek E, Wang L, Kallenbach NR, J Mol Biol. 1999 May 14;288(4):743-52. PMID:10329176 Page seeded by OCA on Fri May 2 12:37:58 2008
