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Updated: Jul 22, 2026

Combining X-Ray Crystallography with Small Angle X-Ray Scattering to Model Unstructured Regions of Nsa1 from S. Cerevisiae
Published on: January 10, 2018
X-ray structure analysis of a designed oligomeric miniprotein reveals a discrete quaternary architecture
Mayssam H Ali1, Ezra Peisach, Karen N Allen
1Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA.
Abstract:
The x-ray crystal structure of an oligomeric miniprotein has been determined to a 1.2-A resolution by means of multiwavelength anomalous diffraction phasing with selenomethionine analogs that retain the biophysical characteristics of the native peptide. Peptide 1, comprising alpha and beta secondary structure elements with only 21 aa per monomer, associates as a discrete tetramer. The peptide adopts a previously uncharacterized quaternary structure in which alpha and beta components interact to form a tightly packed and well defined hydrophobic core. The structure provides insight into the origins of the unusual thermal stability of the oligomer. The miniprotein shares many characteristics of larger proteins, including cooperative folding, lack of 1-anilino-8-naphthalene sulfonate binding, and limited deuterium exchange, and possesses a buried surface area typical of native proteins.
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