title: Transport of alpha-helical peptides through alpha-hemolysin and aerolysin pores.
abstract: A series of negatively charged alpha-helical peptides of the general formula fluorenylmethoxycarbonyl (Fmoc)-D(x)A(y)K(z) were synthesized, where x and z were 1, 2, or 3 and y was 10, 14, 18, or 22. The translocation of the peptides through single pores, which were self-assembled into lipid membranes, was analyzed by measuring the current blockade i(block) and the duration t(block). The pores were either alpha-hemolysin, which has a wide vestibule leading into the pore, or aerolysin, which has no vestibule but has a longer pore of a similar diameter. Many thousands of events were measured for each peptide with each pore, and they could be assigned to two types: bumping events (type I) have a small i(block) and long t(block), and translocation events (type II) have a larger i(block) and shorter t(block). For type-II events, both i(block) and t(block) increase with the length of the peptides on both pores tested. The dipole moment and the net charge of each peptide has a major effect on the transport characteristics. The ratio of type-II/type-I events increases as the dipole moment increases, and uncharged peptides gave mostly type-I events. The structural differences between the two nanopores were reflected in the characteristic values of i(block), and in particular, the vestibule of alpha-hemolysin helps to orient the peptides for translocation. Overall, the results demonstrate that the nanopore technology can provide useful structural information but peptide sequencing will require further improvements in the design of the pores.
authors.affiliation: Department of Biochemistry, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E5, Canada.
authors.forename: Radu
authors.initials: R
authors.lastname: Stefureac
authors.forename: Yi-Tao
authors.initials: YT
authors.lastname: Long
authors.forename: Heinz-Bernhard
authors.initials: HB
authors.lastname: Kraatz
authors.forename: Peter
authors.initials: P
authors.lastname: Howard
authors.forename: Jeremy S
authors.initials: JS
authors.lastname: Lee
mesh_terms: D016980:Aeromonas hydrophila / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D001427:Bacterial Toxins / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D006460:Hemolysin Proteins; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism*; D052899:Pore Forming Cytotoxic Proteins; D017433:Protein Structure, Secondary; D021381:Protein Transport; D013211:Staphylococcus aureus / Q000737:chemistry / Q000378:metabolism; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D001427:Bacterial Toxins; D006460:Hemolysin Proteins; D008051:Lipid Bilayers; D010455:Peptides; D052899:Pore Forming Cytotoxic Proteins; C021091:staphylococcal alpha-toxin; C032676:aerolysin