The spectral and thermodynamic properties of staphylococcal enterotoxin A,E, and variants suggest that structural modifications are important to control their function

Citation
A. Cavallin et al., The spectral and thermodynamic properties of staphylococcal enterotoxin A,E, and variants suggest that structural modifications are important to control their function, J BIOL CHEM, 275(3), 2000, pp. 1665-1672
Citations number
30
Categorie Soggetti
Biochemistry & Biophysics
Journal title
JOURNAL OF BIOLOGICAL CHEMISTRY
ISSN journal
00219258 → ACNP
Volume
275
Issue
3
Year of publication
2000
Pages
1665 - 1672
Database
ISI
SICI code
0021-9258(20000121)275:3<1665:TSATPO>2.0.ZU;2-P
Abstract
The superantigens staphylococcal enterotoxin A and E (SEA and SEE) can acti vate a large number of T-cells, SEA and SEE have approximately 80% sequence identity but show some differences in their biological function. Here, the two superantigens and analogues were characterized biophysically. SEE was shown to have a substantially higher thermal stability than SEA. Both SEA a nd SEE were thermally stabilized by 0.1 mm Zn2+ compared with Zn2+-reduced conditions achieved using 1 1 mm EDTA or specific replacements that affect Zn2+ coordination. The higher stability of SEE was only partly caused by th e T-cell receptor (TCR) binding regions, whereas regions in the vicinity of the major histocompatibility complex class II binding sites affected the s tability to a greater extent, SEE exhibited a biphasic denaturation between pH 5.0-6.5, influenced by residues in the TCR binding regions. Interesting ly, enzyme-linked immunosorbent assay, isoelectric focusing, and circular d ichroism analysis indicated that conformational changes had occurred in the SEA/E chimerical constructs relative to SEA and SEE. Thus, it is proposed that the Zn2+ binding site is very important for the stability and potency of SEA and SEE, whereas residues in the TCR binding site have a substantial influence on the molecular conformation to control specificity and functio n.