Rate-Limiting Endonucleolytic Cleavage of the 2.7 kb puf mRAN of Rhodobacter Capsulatus is Influenced by Oxygen
Segmental differences in the stability of a polycistronic mRNA were first described for the R. capsulatus puf operon (Belasco et al., 1985). The proximal and distal segments of a 2.7 kb mRNA species encoding reaction center (RC) and light harvesting I (LHI) proteins are degraded at different rates, causing a tenfold molar excess of mRNA encoding LHI versus mRNA encoding RC proteins. The higher stability of the LHI-specific 0.5 kb mRNA segment results from protection against 3′ to 5′ exonucleases by an intercistronic mRNA region of secondary structure localized between the LHI genes (pufB, pufA) and the RC genes (pufL, pufM). Removal of this hairpin loop structure results in a change in the molar ratio of the 2.7 kb mRNA species and its 0.5 kb derivative and an altered stoichiometry of LHI and RC complexes in the membrane (Klug et al., 1.987).
KeywordsReaction Center Phototrophic Bacterium Reaction Center Complex Segmental Difference Endonucleolytic Cleavage
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