Analysis of conformational changes in bacteriorhodopsin upon retinal removal.
The conformation of bacterioopsin in the apomembrane has been studied by Fourier transform infrared spectroscopy. Resolution enhancement techniques and curve-fitting procedures have been used to determine the secondary structural components from the amide I region. Bacterioopsin contains about 54% helicoidal structure (alpha I and alpha II helices + 3(10) turns), 21% sheets, 16% reverse turns, and 9% unordered structure. Thus, after retinal removal, all of the secondary structural types of bacteriorhodopsin remain present, and only slight quantitative differences appear. On the other hand, H/D exchange studies show that there is a higher degree of exchange for reverse turns and protonated carboxylic lateral chains in bacterioopsin as compared to bacteriorhodopsin. This gives further support to the idea of a more open tertiary structure of bacterioopsin, and to the consideration of the retinal molecule as an important element in complementing the interhelical interactions in bacteriorhodopsin folding.
Cladera
J
J
Departament de Bioquímica i de Biologia Molecular, Facultat de Medicina, Universitat Autònoma de Barcelona, Bellaterra, Spain.
Torres
J
J
Padrós
E
E
D001436:Bacteriorhodopsins / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D055592:Biophysical Phenomena; D001703:Biophysics; D006217:Halobacterium / Q000378:metabolism; D010777:Photochemistry; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D012172:Retinaldehyde / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
D001436:Bacteriorhodopsins; D012172:Retinaldehyde