2n67

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== Publication Abstract from PubMed ==
== Publication Abstract from PubMed ==
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Pathogenic bacteria secrete pore-forming toxins (PFTs) to selectively defend against immune cells and to break through cellular barriers in the host. Understanding how PFTs attack cell membranes is not only essential for therapeutic intervention but for designing agents to deliver drugs to specific human cell subtypes, for example in anti-cancer or anti-viral therapies. Many toxins contain accessory domains that help recognize specific molecular epitopes on the membranes of target cells, including proteins, carbohydrates, and lipids. Here we report NMR assignments for the 94-residue 10 kDa C-terminal accessory domain of Bacillus cereus hemolysin II, HlyIIC, that has no known structural or functional homologues. The HlyIIC domain exists in a dynamic equilibrium due to cis/trans isomerization of its Gly86-Pro87 peptide bond. The cis and trans forms are about equally populated and are in slow exchange on the NMR timescale, giving rise to separate signals for approximately half of the residues in the domain. Assignments for the cis and trans forms were achieved with the aid of a P87M mutant that stabilizes the trans form, and separate sequential walks for the two forms in 3D NMR spectra of the wild-type HlyIIC. Based on backbone chemical shifts, the domain has a alpha1-alpha2-beta1-beta2-beta3-beta4-alpha3-beta5 order of secondary structure elements. The last strand in the trans form and in the P87M mutant is shortened near Pro87 compared to the cis form. Both cis/trans isomerization and the P87M mutation cause large chemical shift changes throughout HlyIIC, suggesting that the proline is important in stabilizing the structure of the domain. The NMR assignments pave the way for solving the structures of the multiple conformational forms of HlyIIC and establishing their mechanism of interconversion.
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In addition to multiple virulence factors, Bacillus cereus a pathogen that causes food poisoning and life-threatening wound infections, secretes the pore-forming toxin hemolysin II (HlyII). The HlyII toxin has a unique 94 amino acid C-terminal domain (HlyIIC). HlyIIC exhibits splitting of NMR resonances due to cis/trans isomerization of a single proline near the C-terminus. To overcome heterogeneity, we solved the structure of P405M-HlyIIC, a mutant that exclusively stabilizes the trans state. The NMR structure of HlyIIC reveals a novel fold, consisting of two subdomains alphaA-beta1-beta2 and beta3-beta4-alphaB-beta5, that come together in a barrel-like structure. The barrel core is fastened by three layers of hydrophobic residues. The barrel end opposite the HlyIIC-core has a positively charged surface, that by binding negatively charged moieties on cellular membranes, may play a role in target-cell surface recognition or stabilization of the heptameric pore complex. In the WT domain, dynamic flexibility occurs at the N-terminus and the first alpha-helix that connects the HlyIIC domain to the HlyII-core structure. In the destabilizing P405M mutant, increased flexibility is evident throughout the first subdomain, suggesting that the HlyIIC structure may have arisen through gene fusion.
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NMR assignments for the cis and trans forms of the hemolysin II C-terminal domain.,Kaplan AR, Maciejewski MW, Olson R, Alexandrescu AT Biomol NMR Assign. 2014 Oct;8(2):419-23. PMID:24234348<ref>PMID:24234348</ref>
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NMR structure of the Bacillus cereus hemolysin II C-terminal domain reveals a novel fold.,Kaplan AR, Kaus K, De S, Olson R, Alexandrescu AT Sci Rep. 2017 Jun 12;7(1):3277. doi: 10.1038/s41598-017-02917-4. PMID:28607368<ref>PMID:28607368</ref>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>
From MEDLINE&reg;/PubMed&reg;, a database of the U.S. National Library of Medicine.<br>

Revision as of 08:33, 3 August 2017

C-terminal domain of Hemolysin II-P87M-BMRB

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