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Crystal structure of a designed, thermostable, heterotrimeric coiled coil

Published online by Cambridge University Press:  01 January 1999

SHIVANI NAUTIYAL
Affiliation:
Department of Molecular and Cell Biology, 229 Stanley Hall, University of California, Berkeley, California 94720-3206
TOM ALBER
Affiliation:
Department of Molecular and Cell Biology, 229 Stanley Hall, University of California, Berkeley, California 94720-3206
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Abstract

Electrostatic interactions are often critical for determining the specificity of protein-protein complexes. To study the role of electrostatic interactions for assembly of helical bundles, we previously designed a thermostable, heterotrimeric coiled coil, ABC, in which charged residues were employed to drive preferential association of three distinct, 34-residue helices. To investigate the basis for heterotrimer specificity, we have used multiwavelength anomalous diffraction (MAD) analysis to determine the 1.8 Å resolution crystal structure of ABC. The structure shows that ABC forms a heterotrimeric coiled coil with the intended arrangement of parallel chains. Over half of the ion pairs engineered to restrict helix associations were apparent in the experimental electron density map. As seen in other trimeric coiled coils, ABC displays acute knobs-into-holes packing and a buried anion coordinated by core polar amino acids. These interactions validate the design strategy and illustrate how packing and polar contacts determine structural uniqueness.

Type
Research Article
Copyright
© 1999 The Protein Society

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