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Updated: Mar 3, 2026

Combining Wet and Dry Lab Techniques to Guide the Crystallization of Large Coiled-coil Containing Proteins
Published on: January 6, 2017
3-2-1: Structural insights from stepwise shrinkage of a three-helix Fc-binding domain to a single helix
M Ultsch1, A Braisted2, H R Maun3
1Department of Structural Biology, Genentech Inc., 1 DNA Way, South San Francisco, CA 94080,USA.
Abstract:
The well-studied B-domain from Staphylococcal protein A is a 59 amino acid three-helix bundle that binds the Fc portion of IgG with a dissociation constant of ~35 nM. The B-domain variant bearing a Gly to Ala mutation (=Z-domain) has been the subject of efforts to minimize a domain's size while retaining its function. We report X-ray crystallographic characterization of three steps in such a process using complexes with Fc: the full three-helix Z-domain, a 34 amino acid two-helix version called Z34C and a 13 amino acid single helix stabilized with an exo-helix tether, called LH1.
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