Definition: In this task, you're given a paragraph from the research paper and your task is to generate a suitable title for the research paper based on the given paper. Under 100 words is a good title length.
Input: Cholera toxin (CT) from Vibrio cholerae is responsible for the majority of the symptoms of the diarrheal disease cholera. CT is a heterohexameric protein complex with a 240-residue A subunit and a pentameric B subunit of identical 103-residue B polypeptides. The A subunit is proteolytically cleaved within a disulfide-linked loop to generate the A1 and A2 fragments. The B subunit of wild-type (wt) CT binds 5 cell surface ganglioside GM 1 (GM 1 ) molecules, and the toxin-GM 1 complex traffics from the plasma membrane (PM) retrograde through endosomes and the Golgi apparatus to the endoplasmic reticulum (ER). From the ER, the enzymatic A1 fragment retrotranslocates to the cytosol to cause disease. Clustering of GM 1 by multivalent toxin binding can structurally remodel cell membranes in ways that may assist toxin uptake and retrograde trafficking. We have recently found, however, that CT may traffic from the PM to the ER by exploiting an endogenous glycosphingolipid pathway (A. A. Wolf et al., Infect. Immun. 76:1476 -1484, 2008, and D. J. F. Chinnapen et al., Dev. Cell 23:573-586, 2012) , suggesting that multivalent binding to GM 1 is dispensable. Here we formally tested this idea by creating homogenous chimeric holotoxins with defined numbers of native GM 1 binding sites from zero (nonbinding) to five (wild type). We found that a single GM 1 binding site is sufficient for activity of the holotoxin. Therefore, remodeling of cell membranes by mechanisms that involve multivalent binding of toxin to GM 1 receptors is not essential for toxicity of CT. We tested this idea directly by using purified variants of CT with zero to five functional receptor-binding sites (BS). One BS enabled CT to intoxicate cells, supporting the conclusion that CT can enter cells by coopting an endogenous lipid-sorting pathway. Although multivalent receptor binding is not essential, it does increase CT toxicity. These findings suggest that achieving higher receptor binding avidity or affecting membrane dynamics by lipid clustering and membrane remodeling may be driving forces for evolution of AB 5 subunit toxins that can bind multivalently to cell membrane lipid receptors. Citation Jobling MG, Yang Z, Kam WR, Lencer WI, Holmes RK. 2012. A single native ganglioside GM 1 -binding site is sufficient for cholera toxin to bind to cells and complete the intoxication pathway. mBio 3(6):e00401-12.

A Single Native Ganglioside GM 1 -Binding Site Is Sufficient for Cholera Toxin To Bind to Cells and Complete the Intoxication Pathway