Bacterioopsin-triggered retinal biosynthesis is inhibited by bacteriorhodopsin formation in Halobacterium salinarium

Citation
A. Deshpande et S. Sonar, Bacterioopsin-triggered retinal biosynthesis is inhibited by bacteriorhodopsin formation in Halobacterium salinarium, J BIOL CHEM, 274(33), 1999, pp. 23535-23540
Citations number
35
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biochemistry & Biophysics
Journal title
JOURNAL OF BIOLOGICAL CHEMISTRY
ISSN journal
0021-9258 → ACNP
Volume
274
Issue
33
Year of publication
1999
Pages
23535 - 23540
Database
ISI
SICI code
0021-9258(19990813)274:33<23535:BRBIIB>2.0.ZU;2-3
Abstract
Factors regulating retinal biosynthesis in halobacteria are not clearly und erstood. In halobacteria, events leading to the biosynthesis of bacteriorho dopsin have been proposed to participate in stringent regulation of retinal biosynthesis, The present study describes a novel approach of in vivo intr oductions of mRNA and membrane proteins via liposome fusion to test their r ole in cellular metabolism. Both the bacterioopsin-encoding mRNA and the li posome-encapsulated bacterioopsin (apoprotein) are independently introduced in spheroplasts of the purple membrane-negative strain Halobacterium salin arium that initially contain neither bacterioopsin nor retinal, Isoprenoid analyses of these cells indicate that the expression/presence of bacterioop sin triggers retinal biosynthesis from lycopene, and its subsequent binding to opsin generates bacteriorhodopsin, When bacteriorhodopsin and excess re tinal were independently introduced into spheroplasts of purple membrane-ne gative cells, the introduction of bacteriorhodopsin resulted in an accumula tion of lycopene, indicating an inhibition of retinal biosynthesis, These r esults provide direct evidence that the formation of bacterioopsin acts as a trigger for lycopene conversion to beta-carotene in retinal biosynthesis. The trigger for this event does not lie with either transcription or trans lation of the bop gene, It is clearly associated with the folded and the me mbrane-integrated state of bacterioopsin. On the other hand, the trigger si gnaling inhibition of retinal biosynthesis does not lie with the presence o f excess retinal but with the correctly folded, retinal-bound form, bacteri orhodopsin.