X-ray structure analysis of a designed oligomeric miniprotein reveals a discrete quaternary architecture

doi:10.1073/pnas.0401245101

X-ray structure analysis of a designed oligomeric miniprotein reveals a discrete quaternary architecture

^*Departments of Chemistry and Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139; and ^†Department of Physiology and Biophysics, Boston University School of Medicine, 715 Albany Street, Boston, MA 02118

Edited by David S. Eisenberg, University of California, Los Angeles, CA (received for review February 22, 2004)

Abstract

The x-ray crystal structure of an oligomeric miniprotein has been determined to a 1.2-Å resolution by means of multiwavelength anomalous diffraction phasing with selenomethionine analogs that retain the biophysical characteristics of the native peptide. Peptide 1, comprising α and β secondary structure elements with only 21 aa per monomer, associates as a discrete tetramer. The peptide adopts a previously uncharacterized quaternary structure in which α and β 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.

Footnotes

↵ ‡ To whom correspondence may be addressed. E-mail: allen{at}med-xtal.bu.edu or imper{at}mit.edu.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations: DapBz, benzoylated l-α,β-diaminopropionic acid; MAD, multiwavelength anomalous diffraction; SeMet, selenomethionine.
Data deposition: The coordinates of the refined structures have been deposited in the Protein Data Bank, www.pdb.org [PDB ID codes 1SN9 (1), 1SNA (2), and 1SNE (3)].