Direct observation of different surface structures on high-resolution images of native halorhodopsin

Halorhodopsin (HR) was investigated with atomic force microscopic techniques (AFM) in aqueous solution. Two-dimensional (2D) crystals of HR were obtained by purifying an HR membrane fraction with the same buoyant density as the purple membrane (HR-PM) from the overexpressing strain Halobacterium sal...

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Bibliographic Details
Published in:Journal of molecular biology 2001-07, Vol.310 (4), p.773-780
Main Authors: Persike, Norbert, Pfeiffer, Matthias, Guckenberger, Reinhard, Radmacher, Manfred, Fritz, Monika
Format: Article
Language:English
Subjects:
Aluminum Silicates
Amino Acid Sequence
atomic force microscopy
Bacteriorhodopsins - chemistry
Bacteriorhodopsins - metabolism
Bacteriorhodopsins - ultrastructure
Cell Membrane - chemistry
Crystallization
direct imaging
force-induced conformational changes
Halobacterium salinarum - chemistry
Halobacterium salinarum - cytology
halorhodopsin
Halorhodopsins
Microscopy, Atomic Force
Molecular Sequence Data
native proteins
Pliability
Protein Structure, Quaternary
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Summary:Halorhodopsin (HR) was investigated with atomic force microscopic techniques (AFM) in aqueous solution. Two-dimensional (2D) crystals of HR were obtained by purifying an HR membrane fraction with the same buoyant density as the purple membrane (HR-PM) from the overexpressing strain Halobacterium salinarum D2. The membrane patches of HR were immobilized on mica. Images with a resolution up to 14 Å were recorded. Crystals showed an orthogonal structure and the orientation of the molecules showed p42 12 symmetry; thus, alternate tetramers are inverted in the membrane. The crystal surface was found to display different structures depending on the imaging force used, indicating that some parts of the HR molecule are more rigid but others more compressible. From samples with single tetramers missing in the crystalline patches dimensions of the unit cell could be determined. Helix-connecting loops in single molecules of halorhodopsin were assigned. The images indicate that the large extracellular BC loop covers the whole molecule and is very flexible.
ISSN:0022-2836
1089-8638
DOI:10.1006/jmbi.2001.4782