Cloning of carotenoid biosynthesis genes fromRhodopseudomonas sphaeroides

Two cosmids, pJP1433 and pJP1488, have been constructed which carry between them 60 kilobases of the central section of the photosynthesis region ofRhodopseudomonas sphaeroides. Within this region is a segment of some 15 kilobases which encompasses the known carotenoid biosynthesis genesCrtA,CrtB,CrtC,CrtD,CrtE, andCrtF.     

Effects of Ethanol, Temperature, and Endogenous Regulatory Factors on the Characteristics of Striatal Opiate Receptors

Ethanol can alter the affinity of mouse striatal opiate receptors for their ligands, and the present studies were aimed at determining the importance of the receptor microenvironment for this effect of ethanol. Changing the temperature of the binding assay, and thus altering the properties of neuronal membrane lipids, resulted in changes in the observed affinity of striatal binding sites for dihydromorphine (DHM), but not for D-Ala2, D-Leu5-enkephalin (ENK). The changes in temperature also differentially altered the response of the two binding sites to ethanol. Two other factors that regulate opiate receptor affinity, Na+ and GTP, also affected the response to ethanol. High concentrations of ethanol were more effective at decreasing receptor affinity for both DHM and ENK when the binding assays were performed in the presence of GTP or Na+. In addition, at 37 degrees C and in the presence of GTP or Na+, DHM binding, but not ENK binding, was significantly inhibited by a low, physiologically attainable concentration of ethanol. Our results suggest that the response of opiate receptors to ethanol is influenced by the microenvironment of the receptors, including the physical state of the membrane lipids and/or by the nature of the interactions of receptors with "coupling proteins" within the membrane. The differential responses of mu and delta receptors to temperature and to ethanol suggest that these receptors reside in specific membrane environments. Under physiological conditions, several different factors may contribute to a selective action of ethanol on particular subtypes of opiate receptors.     

Expression ofRhodopseudomonas sphaeroides carotenoid photopigment genes in phylogenetically related nonphotosynthetic bacteria

The carotenoid photopigment genes of the purple nonsulfur photosynthetic bacteriumRhodospeudomonas sphaeroides have been cloned into the kanamycin resistance transposon Tn5 to create a carotenoid transposon-Tn5-Crt⁺. Transposition of Tn5-Crt⁺ onto the broad host range plasmid pR751 produced a broad host range carotenoid plasmid-pJP115. Transfer of pJP115 to the phylogenetically related nonphotosynthetic bacteriaParacoccus denitrificans, Agrobacterium tumefaciens, Agrobacterium radiobacter, andAzotomonas insolita resulted in carotenoid biosynthesis by these strains. Expression of carotenoid photopigment genes in nonphotosynthetic bacteria lends credence to the evolutionary relationships between photosynthetic and non-photosynthetic bacteria.