The interaction of a histidine-rich protein hpn with the membrane mimics: implications for pathologic roles of Hpn in Helicobacter pylori.
BACKGROUND
Hpn is a small histidine-rich protein in Helicobacter pylori. This protein has been shown to play roles in nickel storage and detoxification and to exhibit cytotoxicity to gastric epithelial cells. Hpn can be secreted outside of the bacterium and forms amyloid-like structures.


OBJECTIVE
To study the interactions between Hpn and membrane mimics, which may further our understanding of the pathologic roles of this bacterium.


METHODS
Various biochemical and biophysical methods, such as secondary structure determination be CD, calcein release assay with fluorescence spectrometry, and Laurdan and Prodan generalized polarization determination have been used to characterize the interaction between Hpn and membrane mimics.


RESULTS
Membrane mimics induced the formation of α-helix in Hpn. The interaction disrupts the integrity of the membrane mimics and leads to the release of inner calcein probe. The experiments involving the Laurdan and Prodan fluorescence indicated that increasing the total protein/lipid ratio leads to a less ordered and more hydrated lipid membrane structure close to the water/lipid interface of lipid bilayers modeling the mitochondrial inner membrane.


CONCLUSIONS
The present data indicated that Hpn may take part in the pathological roles of Helicobacter pylori through membrane interactions.
Key Laboratory of Gene Engineering of the Ministry of Education, State Key Laboratory of Biocontrol, College of Life Sciences, Sun Yat-Sen University, Guangzhou, China.
Qinglu
Q
Zhou
Shuang
S
Qi
Xuesong
X
Sun
Ruiguang
R
Ge
D001426:Bacterial Proteins / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D005452:Fluoresceins / Q000032:analysis; D005454:Fluorescence Polarization; D016481:Helicobacter Infections / Q000382:microbiology / Q000473:pathology; D016480:Helicobacter pylori / Q000378:metabolism*; D006801:Humans; D008051:Lipid Bilayers / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D011138:Polytetrafluoroethylene / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000378:metabolism*; D014270:Trifluoroethanol / Q000737:chemistry; D000099053:Histidine-Rich Glycoprotein
D001426:Bacterial Proteins; D005452:Fluoresceins; C000597021:Hpn protein, Helicobacter pylori; D008051:Lipid Bilayers; D008565:Membrane Proteins; D011506:Proteins; D000099053:Histidine-Rich Glycoprotein; D014270:Trifluoroethanol; D011138:Polytetrafluoroethylene; C007740:fluorexon
Helicobacter pylori; Hpn; generalized polarization; membrane