Abstract
The functional activity of superantigens is based on capacity of these microbial proteins to bind to both the β-chain of the T cell receptor (TcR) and the major histocompatibility complex (MHC) class II dimer. We have previously shown that a subset of the bacterial superantigens also binds to a membrane protein, designated p85, which is expressed by renal epithelial cells. This binding activity is a property of SEB, SEC1, 2 and 3, but not SEA, SED, SEE or TSST. The crystal structure of the tri-molecular complex of the superantigen staphylococcal enterotoxin B (SEB) with both the TcR and class II has previously been reported. However, the relative contributions of regions of the superantigen to the overall functional activity of this superantigen remain undefined. In an effort to better define the molecular basis for the interaction of SEB with the TcR β-chain, we report studies here which show the comparative contributions of amino- and carboxy-terminal regions in the superantigen activity of SEB. Recombinant fusion proteins composed of bacterial maltose-binding protein linked to either full-length or truncated toxins in which the 81 N-terminal, or 19 or 34 C-terminal amino acids were deleted, were generated for these studies. This approach provides a determination of the relative strength of the functional activity of the various regions of the superantigen protein.
Highlights
The staphylococcal enterotoxins are members of a family of gram-positive pyrogenic exotoxins possessing superantigen activity
The staphylococcal enterotoxins, toxic syndrome shock toxin-1 (TSST-1), and streptococcal pyrogenic exotoxins are structurally related proteins [1,2,3]. These bacterial superantigens possess two common properties. They bind with moderate affinity to major histocompatibility complex (MHC) class II dimers [4,5], and second, these toxins are recognized by the T cell receptor (TcR) in a β-chain variable region allele-selective fashion [6,7]
The cΔ19SEB-maltose-binding protein (MBP) fusion induced a response which was less than 20% of that observed with the full-length fusion (ED50 for cΔ19SEB-MBP: 900 pmol)
Summary
The staphylococcal enterotoxins are members of a family of gram-positive pyrogenic exotoxins possessing superantigen activity. Additional work [41] has shown that deletion of as few as 60 N-terminal amino acids results in greatly impaired SEB activity It is clear, from the solution of the crystal structures of SEB [27] that the C-terminus of these bacterial superantigens folds back onto the N-terminal residues. Our results provide further information regarding the participation of both N-terminal and C-terminal residues in the superantigen activity of this toxin, and demonstrate that MBP fusions can be utilized to assess the functional activities of these microbial toxins
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
