Open AccessStructure of a mutant β toxin from Staphylococcus aureus reveals domain swapping and conformational flexibility
Author(s) -
Kruse Andrew C.,
Huseby Medora J.,
Shi Ke,
Digre Jeff,
Ohlendorf Douglas H.,
Earhart Cathleen A.
Publication year - 2011
Publication title -
acta crystallographica section f
Language(s) - English
Resource type - Journals
ISSN - 1744-3091
DOI - 10.1107/s1744309111005239
Subject(s) - mutant , monomer , crystallography , crystal structure , molecule , chemistry , stereochemistry , intermolecular force , molecular replacement , protein structure , biophysics , biology , biochemistry , polymer , organic chemistry , gene
The 3.35 Å resolution crystal structure of a mutant form of the staphylococcal sphingomyelinase β toxin in which a conserved hydrophobic β‐hairpin has been deleted is reported. It is shown that this mutation induces domain swapping of a C‐terminal β‐strand, leading to the formation of dimers linked by a conformationally flexible hinge region. Eight dimers are seen in the asymmetric unit, exhibiting a broad spectrum of conformations trapped in place by intermolecular contacts within the crystal lattice. Furthermore, the 16 monomers within each asymmetric unit exhibit a remarkable heterogeneity in thermal factors, which can be accounted for by the varying degrees to which each monomer interacts with other molecules in the crystal. This structure provides a unique example of the challenges associated with crystallographic study of flexible proteins.