The structure of mutant bacteriorhodopsin (bR), D85N, was examined by
CD and X-ray diffraction at pH 7. The absorption maximum of D85N at pH
7 is located at 605 nm, which is similar to the acid-blue form of wil
d-type bR. D85N shows a monophasic CD band, the maximum of which is at
575 nm, although the crystalline arrangement and the trimeric structu
re is maintained. The acid-blue form of wild-type bR shows a biphasic
CD despite the similarity in absorption spectra.