title: Circular dichroism and molecular modeling of the E. coli TolA periplasmic domains.
abstract: Colicins are killer proteins that use envelope proteins from the outer and the inner membranes to reach their cellular target in susceptible cells of Escherichia coli. Each group A colicin uses a combination of Tol proteins to cross the outer membrane of gram-negative bacteria and to exert their killing activity. The TolA protein, necessary for the import of all the group A colicins, is a 421-amino acid residue protein composed of three domains (TolAI, TolAII, and TolAIII). TolAIII interacts with the N-terminal domain of colicin A (AT1). Analytical ultracentrifugation reveals that TolAII and TolAIII are monomer structures, TolAII has an elongated structure, and TolAIII is rather globular. Circular dichroism (CD) spectra were done with TolAII-III, TolAII, TolAIII, AT1, and the AT1-TolAII-III complex. TolA CD spectra reveal the presence of alpha-helix structure in aqueous solution and the intensity of the a-helix signal is the highest with TolAII. Few structural changes are observed with the complex AT1-TolAII-III. Molecular modeling was done for TolAII-III, taking into account CD and ultracentrifugation data and show that domain II can adopt a barrel structure made of three twisted alpha-helices similar to coiled coil helices while domain III can adopt a globular structure.
authors.affiliation: Laboratoire d'Ingénierie des Systèmes Macromoléculaires, CNRS UPR 9027, Institut de Biologie Structurale et Microbiologie, Marseille, France.
authors.forename: R
authors.initials: R
authors.lastname: Derouiche
authors.forename: R
authors.initials: R
authors.lastname: Lloubès
authors.forename: S
authors.initials: S
authors.lastname: Sasso
authors.forename: H
authors.initials: H
authors.lastname: Bouteille
authors.forename: R
authors.initials: R
authors.lastname: Oughideni
authors.forename: C
authors.initials: C
authors.lastname: Lazdunski
authors.forename: E
authors.initials: E
authors.lastname: Loret
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism; D002498:Centrifugation; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D003087:Colicins / Q000737:chemistry / Q000378:metabolism; D004926:Escherichia coli / Q000737:chemistry; D029968:Escherichia coli Proteins; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D019897:Periplasm / Q000737:chemistry*; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification
chemical_list: D001426:Bacterial Proteins; D003087:Colicins; D029968:Escherichia coli Proteins; D010446:Peptide Fragments; D011994:Recombinant Proteins; C062093:tolA protein, E coli