Helical and reverse turn changes in the BR arrow right N transition of bacteriorhodopsin

• Published in: Biochemistry (Easton) Vol. 35; no. 25; pp. 8354 - 8358
• Main Authors: Lazarova, T, Padros, E
• Format: Journal Article
• Language: English
• Published: 01.01.1996
• ISSN: 0006-2960

Fourier transform infrared deconvoluted spectra of bacteriorhodopsin and the N intermediate were compared with the N/BR infrared difference spectrum. In the amide I, clear changes in the bands at 1666/cm, assigned to alpha sub(II) helices, 1659/cm, assigned to alpha sub(I) and alpha sub(II), helices, and 1652/cm, assigned to both alpha sub(I) helices and unordered structures, were found. These changes could arise from conversion of some alpha sub(II) into alpha sub(I) helices. Variations in the bands at 1692 and 1683/cm, corresponding to reverse turns, were also detected. The side chains of Tyr (band at 1517/cm) and Phe (band at 1498/cm) were found to change in going from BR to N. In the carboxylate region, no band was detected at 1737 cm super(-1) in the deconvoluted spectra that could correspond to the peak observed in the difference spectrum. It is argued that resolution-enhancement methods used along with difference spectra provide more detailed insights into the conformational changes occurring between photocycle intermediates.