Structure and interaction of VacA of Helicobacter pylori with a lipid membrane.
In its mature form, the VacA toxin of Helicobacter pylori is a 95-kDa protein which is released from the bacteria as a low-activity complex. This complex can be activated by low-pH treatment that parallels the activity of the toxin on target cells. VacA has been previously shown to insert itself into lipid membranes and to induce anion-selective channels in planar lipid bilayers. Binding of VacA to lipid vesicles and its ability to induce calcein release from these vesicles were systematically compared as a function of pH. These two phenomena show a different pH-dependence, suggesting that the association with the lipid membrane may be a two-step mechanism. The secondary and tertiary structure of VacA as a function of pH and the presence of lipid vesicles were investigated by Fourier-transform infrared spectroscopy. The secondary structure of VacA is identical whatever the pH and the presence of a lipid membrane, but the tertiary structure in the presence of a lipid membrane is dependent on pH, as evidenced by H/D exchange.
Pagliaccia
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C
Centro di Ricerche IRIS, Chiron SpA, Siena, Italy.
Wang
X M
XM
Tardy
F
F
Telford
J L
JL
Ruysschaert
J M
JM
Cabiaux
V
V
D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism*; D003903:Deuterium / Q000378:metabolism; D005452:Fluoresceins / Q000378:metabolism; D016480:Helicobacter pylori / Q000737:chemistry*; D006859:Hydrogen / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry / Q000378:metabolism*; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism; D010743:Phospholipids / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D017550:Spectroscopy, Fourier Transform Infrared
D001426:Bacterial Proteins; D005452:Fluoresceins; D008051:Lipid Bilayers; D008081:Liposomes; D010713:Phosphatidylcholines; D010743:Phospholipids; C074689:VacA protein, Helicobacter pylori; C024990:asolectin; D006859:Hydrogen; D003903:Deuterium; C007740:fluorexon