First post was about halobacteria growing.
This paper relates to biosynthesis of rhodopsin from halobacteria.
Biosynthesis of the Purple Membrane of Halobacteria
By Manfred Sumper, Heribert Reitmeier, and Dieter Oesterhelt[*j
Dedicated to Professor Feodor Ljinen on the occasion of his 65th birthday
Halobacteria are extremely specialized organisms. They live exclusively in saturated solutions
of common salt. The cell membrane of these bacteria exhibit insular regions which can be
isolated by membrane fractionation. These regions consist of a lipid matrix containing bateriorhodopsin
molecules in a hexagonal crystalline arrangement. Bacteriorhodopsin is a deep purple
retinal-protein complex (“purple membrane”). The purple membrane functions as a light energy
converter. --How can such a differentiated membrane region arise? In uiuo studies on the
biosynthesis of the purple membrane showed another cell membrane fraction, the so-called
brown membrane, to be a biosynthetic precursor. Bacterioopsin (the retinal-free protein) is
initially incorporated into the brown membrane and can only form the purple membrane
by crystallization in an energy-dependent reaction after prior reaction with retinal. This reaction
is reversible. Removal of the retinal by formation of retinal oxime causes the purple membrane
regions to disappear. Reconstitution of the bacteriorhodopsin by addition of retinal regenerates
the purple membrane.