Bacteriorhodopsin
Bacteriorhodopsin is a
photosynthetic pigment used by
archaea, most notably
halobacteria. An
integral membrane protein, it belongs to the "
7TM receptor family," so-called because each is composed of seven
transmembrane alpha helices. The
amino acid sequences of the bacteriorhodopsins resemble those of
vertebrate rhodopsins, which are the
pigments that sense light in the
retina. Evidence from
crystallography confirms that the two classes of proteins are also similar in shape or
tertiary structure.