title: A peptide derived from the putative transmembrane domain in the tail region of E. coli toxin hemolysin E assembles in phospholipid membrane and exhibits lytic activity to human red blood cells: plausible implications in the toxic activity of the protein.
abstract: Hemolysin E (HlyE), a pore-forming protein-toxin and a potential virulence factor of Escherichia coli, exhibits cytotoxic activity to mammalian cells. However, very little is known about how the different individual segments contribute in the toxic activity of the protein. Toward this end, the role of a 33-residue segment comprising the amino acid region 88 to 120, which contains the putative transmembrane domain in the tail region of HlyE has been addressed in the toxic activity of the protein-toxin by characterizing the related wild type and mutant peptides and the whole protein. Along with the 33-residue wild type peptide, H-88, two mutants of the same size were synthesized; in one mutant a conserved valine at 89th position was replaced by aspartic acid and in the other both glycine and valine at the 88th and 89th positions were substituted by aspartic acid residues. These mutations were also incorporated in the whole toxin HlyE. Results showed that only H-88 but not its mutants permeabilized both lipid vesicles and human red blood cells (hRBCs). Interestingly, while H-88 exhibited a moderate lytic activity to human red blood cells, the mutants were not active. Drastic reduction in the depolarization of hRBCs and hemolytic activity of the whole toxin HlyE was also observed as a result of the same double and single amino acid substitution in it. The results indicate an important role of the amino acid segment 88-120, containing the putative transmembrane domain of the tail region of the toxin in the toxic activity of hemolysin E.
authors.affiliation: Molecular and Structural Biology Division, Central Drug Research Institute, Lucknow-226001, India.
authors.forename: Sharada Prasad
authors.initials: SP
authors.lastname: Yadav
authors.forename: Aqeel
authors.initials: A
authors.lastname: Ahmad
authors.forename: Brijesh Kumar
authors.initials: BK
authors.lastname: Pandey
authors.forename: Dharamsheela
authors.initials: D
authors.lastname: Singh
authors.forename: Neeta
authors.initials: N
authors.lastname: Asthana
authors.forename: Richa
authors.initials: R
authors.lastname: Verma
authors.forename: Raj Kamal
authors.initials: RK
authors.lastname: Tripathi
authors.forename: Jimut Kanti
authors.initials: JK
authors.lastname: Ghosh
mesh_terms: D000595:Amino Acid Sequence; D002462:Cell Membrane / Q000187:drug effects*; D002463:Cell Membrane Permeability; D004912:Erythrocytes / Q000187:drug effects*; D004926:Escherichia coli / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000633:toxicity*; D006460:Hemolysin Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000633:toxicity*; D006461:Hemolysis / Q000187:drug effects; D006801:Humans; D008567:Membranes, Artificial; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000633:toxicity*; D010743:Phospholipids / Q000737:chemistry*; D016062:Porosity; D016415:Sequence Alignment
chemical_list: D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; D008567:Membranes, Artificial; D010446:Peptide Fragments; D010743:Phospholipids; C119944:hlyE protein, E coli