page_title: Erythrogenic toxin
section_title: Protein structure
hierarchical_section_title: Erythrogenic toxin / Structure / Protein structure
caption_attribution_description: বাংলা: 1pvj কোডসহ নিবন্ধিত প্রোটিনের আণবিক গঠনের কার্টুন উপস্থাপনা। English: Cartoon representation of the molecular structure of protein registered with 1pvj code. Deutsch: Grafik des Molekularstruktur von jenem Protein, das mit 1pvj code registriert ist. Plattdüütsch: Grafik, de de Molekularstruktur von dat Protein wiest, dat mit’n Kood 1pvj registreert is.
context_page_description: Erythrogenic toxins, also referred to as streptococcal pyrogenic exotoxins, are secreted by strains of the bacterium Streptococcus pyogenes. SpeA and speC are superantigens, which induce inflammation by nonspecifically activating T cells and stimulating the production of inflammatory cytokines. SpeB, the most abundant streptococcal extracellular protein, is a cysteine protease. Pyrogenic exotoxins are implicated as the causative agent of scarlet fever and streptococcal toxic shock syndrome. There is no consensus on the exact number of pyrogenic exotoxins. Serotypes A-C are the most extensively studied and recognized by all sources, but others note up to thirteen distinct types, categorizing speF through speM as additional superantigens.
  Erythrogenic toxins are known to damage the plasma membranes of blood capillaries under the skin and produce a red skin rash. Past studies have shown that multiple variants of erythrogenic toxins may be produced, depending on the strain of S. pyogenes in question. Some strains may not produce a detectable toxin at all. Bacteriophage T12 infection of S. pyogenes enables the production of speA, and increases virulence.
context_section_description: SpeB is a 28 kDa protein with three major forms, mSpeB1, mSpeB2 and mSpeB3, which are categorized by variations the primary amino acid sequence. Three amino acids, C192, H340, and W357, are vital for enzymatic activity in all variants. The toxin contains a canonical papain-like domain, and mSpeB2 has an additional human integrin binding domain.
  All superantigenic streptococcal pyrogenic exotoxins contain two major conserved protein domains that are linked by an α-helix, which consist of an amino-terminal oligosoccharide/oligonucleotide binding fold and a carboxy-terminal β-grasp domain, as well as dodecapeptide binding region. SpeA also has a cystine loop, a low-affinity α-chain MHC II binding site, and the Vβ-TCR binding site. SpeC, SpeG, SpeH and SpeJ contains a Zn²⁺-dependent high β-chain MHC II binding site in addition to the low affinity site present in SpeA, and lacks the cystine loop. SpeH also has an additional α3-β8 loop that mediates the specificity of the toxin's Vβ-TCR binding site.
caption: Structure of SpeB.
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