Association of the halobacterial 7S RNA to the polysome correlates with expression of the membrane protein bacterioopsin.

The sedimentation behavior of the halobacterial 7S RNA and bacterioopsin mRNA was assessed after application of total cell lysates to sucrose gradients. These two RNAs cosedimented predominantly with membrane-bound polysomes, and the quantity of 7S RNA bound to the ribosomes was directly correlated with the expression of bacterioopsin. Puromycin treatment released the 7S RNA from the polysomes, indicating that it is transiently associated with protein translation. We suggest that halobacteria contain a signal-recognition-like particle involved in translation of membrane-associated proteins.