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

TY - JOUR

T1 - The spectral and thermodynamic properties of staphylococcal enterotoxin A, E, and variants suggest that structural modifications are important to control their function

AU - Cavallin, Anders

AU - Arozenius, Helena

AU - Kristensson, Karin

AU - Antonsson, Per

AU - Otzen, Daniel E.

AU - Björk, Per

AU - Forsberg, Göran

PY - 2000/1/21

Y1 - 2000/1/21

N2 - The superantigens staphylococcal enterotoxin A and E (SEA and SEE) can activate 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 and SEE were thermally stabilized by 0.1 mM Zn2+ compared with Zn2+- reduced conditions achieved using 1 mM EDTA or specific replacements that affect Zn2+ coordination. The higher stability of SEE was only partly caused by the T-cell receptor (TCR) binding regions, whereas regions in the vicinity of the major histocompatibility complex class II binding sites affected the stability to a greater extent. SEE exhibited a biphasic denaturation between pH 5.0-6.5, influenced by residues in the TCR binding regions. Interestingly, enzyme-linked immunosorbent assay, isoelectric focusing, and circular dichroism 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 function.

AB - The superantigens staphylococcal enterotoxin A and E (SEA and SEE) can activate 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 and SEE were thermally stabilized by 0.1 mM Zn2+ compared with Zn2+- reduced conditions achieved using 1 mM EDTA or specific replacements that affect Zn2+ coordination. The higher stability of SEE was only partly caused by the T-cell receptor (TCR) binding regions, whereas regions in the vicinity of the major histocompatibility complex class II binding sites affected the stability to a greater extent. SEE exhibited a biphasic denaturation between pH 5.0-6.5, influenced by residues in the TCR binding regions. Interestingly, enzyme-linked immunosorbent assay, isoelectric focusing, and circular dichroism 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 function.

UR - http://www.scopus.com/inward/record.url?scp=0034695588&partnerID=8YFLogxK

U2 - 10.1074/jbc.275.3.1665

DO - 10.1074/jbc.275.3.1665

M3 - Journal article

C2 - 10636860

AN - SCOPUS:0034695588

SN - 0021-9258

VL - 275

SP - 1665

EP - 1672

JO - Journal of Biological Chemistry

JF - Journal of Biological Chemistry

IS - 3

ER -