title: Fourier transform infrared evidence for a predominantly alpha-helical structure of the membrane bound channel forming COOH-terminal peptide of colicin E1.
abstract: The structure of the membrane bound state of the 178-residue thermolytic COOH-terminal channel forming peptide of colicin E1 was studied by polarized Fourier transform infrared (FTIR) spectroscopy. This fragment was reconstituted into DMPC liposomes at varying peptide/lipid ratios ranging from 1/25-1/500. The amide I band frequency of the protein indicated a dominant alpha-helical secondary structure with limited beta- and random structures. The amide I and II frequencies are at 1,656 and 1,546 cm-1, close to the frequency of the amide I and II bands of rhodopsin, bacteriorhodopsin and other alpha-helical proteins. Polarized FTIR of oriented membranes revealed that the alpha-helices have an average orientation less than the magic angle, 54.6 degrees, relative to the membrane normal. Almost all of the peptide groups in the membrane-bound channel protein undergo rapid hydrogen/deuterium (H/D) exchange. These results are contrasted to the alpha-helical membrane proteins, bacteriorhodopsin, and rhodopsin.
authors.affiliation: Physics Department, Boston University, Massachusetts 02215.
authors.forename: P
authors.initials: P
authors.lastname: Rath
authors.forename: O
authors.initials: O
authors.lastname: Bousché
authors.forename: A R
authors.initials: AR
authors.lastname: Merrill
authors.forename: W A
authors.initials: WA
authors.lastname: Cramer
authors.forename: K J
authors.initials: KJ
authors.lastname: Rothschild
mesh_terms: D055592:Biophysical Phenomena; D001703:Biophysics; D002462:Cell Membrane / Q000737:chemistry; D003087:Colicins / Q000737:chemistry* / Q000494:pharmacology; D004926:Escherichia coli / Q000032:analysis / Q000187:drug effects; D005583:Fourier Analysis; D007473:Ion Channels / Q000737:chemistry* / Q000187:drug effects; D015394:Molecular Structure; D011487:Protein Conformation; D012995:Solubility; D013055:Spectrophotometry, Infrared; D014867:Water
chemical_list: D003087:Colicins; D007473:Ion Channels; D014867:Water