Circular dichroism and molecular modeling of theE. coli TolA periplasmic domains

Autor: Henri Bouteille, Roland Lloubès, Sophie Sasso, Rahmona Derouiche, Claude Lazdunski, Erwann Loret, R. Oughideni
Rok vydání: 1999
Předmět:
Zdroj: Biospectroscopy. 5:189-198
ISSN: 1520-6343
1075-4261
DOI: 10.1002/(sici)1520-6343(1999)5:3<189::aid-bspy8>3.0.co;2-o
Popis: 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 α-helix structure in aqueous solution and the intensity of the α-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 α-helices similar to coiled coil helices while domain III can adopt a globular structure. © 1999 John Wiley & Sons, Inc. Biospectroscopy 5: 189–198, 1999
Databáze: OpenAIRE
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