These molecules bind to the V-beta chain of T-cell receptors, giving them a greater number of potential targets than those restricted to unique alpha and beta receptor clonotypes. For 10 points each:
[10h] Name these molecules that bind class II MHCs and T-cell receptors outside of the normal peptide-binding groove, resulting in T-cell overactivation. These molecules act as potent exotoxins in scarlet fever.
ANSWER: superantigens [accept SAgs; prompt on antigens]
[10e] Superantigen engagement causes T-cells to activate signaling through the Src (“sark”) family of kinases, which are enzymes that transfer these groups from donors like ATP to their substrates.
ANSWER: phosphates
[10m] In the absence of a Src kinase, SAgs activate T-cells through the activation of phospholipase C by the alpha-11 subunit of these proteins. These proteins couple with receptors that cross the cell membrane seven times.
ANSWER: G proteins [or guanine-nucleotide-binding proteins; accept heterotrimeric G proteins]
<AY, Biology>