Integration of Ganglioside GT1b Receptor into DPPE and DPPC Phospholipid Monolayers: An X-ray Reflectivity and Grazing Incidence Diffraction Study
Chad E Miller 1, David D Busath 2, Bradley Strongin 2 and Jaroslaw Majewski 1*
1 Los Alamos National Laboratory
2 Brigham Young University
* To whom correspondence should be addressed. E-mail: jarek{at}lanl.gov.
Submitted on December 27, 2007
Revised on January 31, 2008
Accepted on 12 June 2008
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Abstract |
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Using synchrotron grazing-incidence x-ray diffraction (GIXD) and reflectivity, the in-plane and out-of-plane structure of mixed ganglioside GT1b-phospholipid monolayers were investigated at the air-liquid interface and compared to monolayers of the pure components. GT1b is involved in binding of lectins and toxins, including botulinum neurotoxin, to cell membranes. Monolayers composed of 20 mol% ganglioside GT1b, the phospholipid dipalmitoylphosphatidylethanolamine (DPPE), and the phospholipid dipalmitoylphosphatidylcholine (DPPC) were studied in the gel phase at 23°C and at surface pressures of 20 and 40 mN/m and at a pH of 7.4 and 5. At these conditions the two components did not phase-separate and no evidence for domain formation was observed. X-ray scattering measurements revealed that GT1b was intercalated within the host DPPE/DPPC monolayers and slightly expanded DPPE but condensed the DPPC matrix. The oligosaccharide headgroups were found to extend normally from the monolayer surfaces into the subphase. These studies demonstrate that these monolayers can serve as platforms to investigate toxin membrane binding and penetration.
Key Words:
GID, GIXD, air-liquid interface, botulinum neurotoxin receptor, grazing incidence x-ray diffraction, protein binding
