Title of article :
Core Side-chain Packing and Backbone Conformation in Lpp-56 Coiled-coil Mutants
Author/Authors :
Jie Liu، نويسنده , , Wei Cao، نويسنده , , Min Lu، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2002
Abstract :
Native proteins exhibit precise geometric packing of atoms in their hydrophobic interiors. Nonetheless, controversy remains about the role of core side-chain packing in specifying and stabilizing the folded structures of proteins. Here we investigate the role of core packing in determining the conformation and stability of the Lpp-56 trimerization domain. The X-ray crystal structures of Lpp-56 mutants with alanine substitutions at two and four interior core positions reveal trimeric coiled coils in which the twist of individual helices and the helix–helix spacing vary significantly to achieve the most favored superhelical packing arrangement. Introduction of each alanine “layer” into the hydrophobic core destabilizes the superhelix by 1.4 kcal mol−1. Although the methyl groups of the alanine residues pack at their optimum van der Waals contacts in the coiled-coil trimer, they provide a smaller component of hydrophobic interactions than bulky hydrophobic side-chains to the thermodynamic stability. Thus, specific side-chain packing in the hydrophobic core of coiled coils are important determinants of protein main-chain conformation and stability.
Keywords :
side-chain packing , coiled coil , protein stability , hydrophobic effect , Crystallography
Journal title :
Journal of Molecular Biology
Journal title :
Journal of Molecular Biology