Peptide-chain secondary structure of bacteriorhodopsin
Journal Article
·
· Biophys. J.; (United States)
Ultraviolet circular dichroism spectroscopy in the interval from 190 to 240 nm and infrared spectroscopy in the region of the amide I band (1600 cm/sup -1/ to 1700 cm/sup -1/) has been used to estimate the ..cap alpha..-helix content and the ..beta..-sheet content of bacteriorhodopsin. Circular dichroism spectroscopy strongly suggests that the ..cap alpha..-helix content is sufficient for only five helices, if each helix is composed of 20 or more residues. It also suggests that there is substantial ..beta..-sheet confirmation in bacteriorhodopsin. The presence of ..beta..-sheet secondary structure is further suggested by the presence of a 1639 cm/sup -1/ shoulder on the amide I band in the infrared spectrum. Although a structural model consisting of seven ..cap alpha..-helical rods has been generally accepted up to this point, the spectroscopic data are more consistent with a model consisting of five ..cap alpha..-helices and four strands of ..beta..-sheet. The primary amino acid sequence can be assigned to segments of ..cap alpha..-helix and ..beta..-sheet in a way that does not require burying more than two charged groups in the hydrophobic membrane interior, contrary to the situation for any seven-helix model.
- Research Organization:
- Lawrence Berkeley Lab., CA
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5009355
- Journal Information:
- Biophys. J.; (United States), Journal Name: Biophys. J.; (United States) Vol. 43; ISSN BIOJA
- Country of Publication:
- United States
- Language:
- English
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