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J Biol Chem 2014 May 02;28918:12805-12. doi: 10.1074/jbc.M113.541896.
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Hemolytic lectin CEL-III heptamerizes via a large structural transition from α-helices to a β-barrel during the transmembrane pore formation process.

Unno H , Goda S , Hatakeyama T .

CEL-III is a hemolytic lectin isolated from the sea cucumber Cucumaria echinata. This lectin is composed of two carbohydrate-binding domains (domains 1 and 2) and one oligomerization domain (domain 3). After binding to the cell surface carbohydrate chains through domains 1 and 2, domain 3 self-associates to form transmembrane pores, leading to cell lysis or death, which resembles other pore-forming toxins of diverse organisms. To elucidate the pore formation mechanism of CEL-III, the crystal structure of the CEL-III oligomer was determined. The CEL-III oligomer has a heptameric structure with a long β-barrel as a transmembrane pore. This β-barrel is composed of 14 β-strands resulting from a large structural transition of α-helices accommodated in the interface between domains 1 and 2 and domain 3 in the monomeric structure, suggesting that the dissociation of these α-helices triggered their structural transition into a β-barrel. After heptamerization, domains 1 and 2 form a flat ring, in which all carbohydrate-binding sites remain bound to cell surface carbohydrate chains, stabilizing the transmembrane β-barrel in a position perpendicular to the plane of the lipid bilayer.

PubMed ID: 24652284
PMC ID: PMC4007468
Article link: J Biol Chem

Genes referenced: LOC100887844 LOC115919910 LOC115925415

References [+] :
, The CCP4 suite: programs for protein crystallography. 2005, Pubmed