FHUA, AN ESCHERICHIA-COLI OUTER-MEMBRANE PROTEIN WITH A DUAL FUNCTIONOF TRANSPORTER AND CHANNEL WHICH MEDIATES THE TRANSPORT OF PHAGE DNA

Citation
M. Bonhivers et al., FHUA, AN ESCHERICHIA-COLI OUTER-MEMBRANE PROTEIN WITH A DUAL FUNCTIONOF TRANSPORTER AND CHANNEL WHICH MEDIATES THE TRANSPORT OF PHAGE DNA, Biochimie, 80(5-6), 1998, pp. 363-369
Citations number
38
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biology
Journal title
ISSN journal
0300-9084
Volume
80
Issue
5-6
Year of publication
1998
Pages
363 - 369
Database
ISI
SICI code
0300-9084(1998)80:5-6<363:FAEOPW>2.0.ZU;2-2
Abstract
FhuA (M-r 78 900) is an Escherichia coli outer membrane protein which transports the ferric siderophore ferrichrome and is the receptor for phage T5, Phi 80 and T1 and for colicin M. FhuA was purified chromatog raphically in non-ionic detergent (octyl glucoside). The circular dich roism spectrum indicates that FhuA is essentially organized in P-stran ds like the majority of proteins of the outer membrane of Gram-negativ e bacteria. The structural parameters of FhuA were assessed from size exclusion chromatography, sedimention equilibrium and velocity experim ents. FhuA is monomeric in solution and functional since binding of ph age T5 causes the release of the phage genome, a double-stranded DNA o f 121 000 base pairs, into the surrounding medium. Planar lipid bilaye r experiments showed that the FhuA transporter is converted into a hig h conductance channel upon binding of phage T5. FhuA was reconstituted into large unilamellar vesicles (mean diameter 125 nm). Cryo-electron microscopy and fluorescence experiments, using a DNA intercalant YO-P RO 1, showed that binding of T5 to FhuA triggers the transfer of the p hage genome into the proteoliposomes without altering their morphology . Two models can account for these observations, which apply both to i n vitro and in vivo DNA transport. The simplest model supposes that th e naked DNA is transported through the FhuA channel. Alternatively tra nsfer of DNA might be mediated by pb2, the protein forming the phage s traight fiber pb2 would insert either directly in the membrane or insi de the FhuA channel ((C) Societe francaise de biochimie et biologie mo leculaire / Elsevier, Paris).