Crystallographic structure determination of staphylococcal enterotoxin type C3 at 1.9 angstrom resolution
Abstract
Staphylococcal enterotoxins, toxic shock syndrome toxin-l and related pyrogenic toxins produced by streptococci have been linked to a variety of toxigenic human illnesses including food poisoning and toxic shock syndrome. These toxins have been categorized as 'superantigens' due to their ability to bind to the class II major histocompatibility complex (MHCII) molecules and the T-cell receptor (TCR) in a fashion independent of the presence of antigen, resulting in massive T-cell proliferation and subsequent cytokine release. The structure of staphylococcal enterotoxin type C3 (SEC3) was determined by X-ray diffraction employing the multiple isomorphous replacement with anomalous scattering (MIRAS) and solvent flattening methods. The initial model was refined to 1.9A resolution using restrained least squares methods. The present model, which includes all 239 residues, a zinc atom and 160 water molecules, gives an R-factor of 17.5% for 15,932 reflections between 20.0 and 1.9A resolution. Except for the central portion of the disulfide loop, all protein atoms have clear density and refined to an average temperature factor of 25.2A$\sp2$. The root-mean-square (rms) deviation of the bond lengths and bond angles from standard values is 0.013A and 2.198$\sp\circ$, respectively and the estimated coordinates error is 0.23A. A detailed description of the SEC3 structure and its functional implications are presented.
Degree
Ph.D.
Advisors
Stauffacher, Purdue University.
Subject Area
Biology|Biophysics|Biochemistry
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