mRNA localization, reaction centre biogenesis and thylakoid membrane targeting in cyanobacteria

The thylakoid membranes of cyanobacteria form a complex intracellular membrane system with a distinctive proteome. The sites of biogenesis of thylakoid proteins remain uncertain, as do the signals that direct thylakoid membrane-integral proteins to the thylakoids rather than to the plasma membrane. Here, we address these questions by using fluorescence in situ hybridization to probe the subcellular location of messenger RNA molecules encoding core subunits of the photosystems in two cyanobacterial species. These mRNAs cluster at thylakoid surfaces mainly adjacent to the central cytoplasm and the nucleoid, in contrast to mRNAs encoding proteins with other locations. Ribosome association influences the distribution of the photosynthetic mRNAs on the thylakoid surface, but thylakoid affinity is retained in the absence of ribosome association. However, thylakoid association is disrupted in a mutant lacking two mRNA-binding proteins, which probably play roles in targeting photosynthetic proteins to the thylakoid membrane

Effect of choline carboxylate ionic liquids on biological membranes

Choline carboxylates, ChCm, with m = 2-10 and choline oleate are known as biocompatible substances, yet their influence on biol. membranes is not well-known, and the effect on human skin has not previously been investigated. The short chain choline carboxylates ChCm with m = 2, 4, 6 act as hydrotropes, solubilizing hydrophobic compds. in aq. soln., while the longer chain choline carboxylates ChCm with m = 8, 10 and oleate are able to form micelles.In the present study, the cytotoxicity of choline carboxylates was tested using HeLa and SK-MEL-28 cells. The influence of these substances on liposomes prepd. from dipalmitoylphosphatidylcholine (DPPC) was also evaluated to provide insights on membrane interactions. It was obsd. that the choline carboxylates with a chain length of m > 8 distinctly influence the bilayer, while the shorter ones had minimal interaction with the liposomes

Low Toxic Ionic Liquids, Liquid Catanionics, and Ionic Liquid Microemulsions

A review. In the future the demand of sustainable and low toxic surfactants and solvents will constantly increase. In this article, we review some new approaches to meet these requirements. Whereas ionic liqs. are often based on imidazolium ions, we will show that there are also much less toxic ones, esp. with choline as cation. Choline salts, even if solid at room temp., can advantageously be mixed with other sustainable solids to form deep eutectic solvents, i.e., "green" liqs. at room temp. Further, choline can be used to dissolve long-chain carboxylates in water thus maybe permitting new applications of soaps. Alternatively, choline and other natural cations can be part of promising low toxic cationic surfactants. By combining them with ethoxylated carboxylates, interesting charged room temp. liq. surfactant combinations can be obtained. Finally, we shortly discuss the potential benefits of ionic liqs. in microemulsions

The PHOTOSYNTHESIS AFFECTED MUTANT68–LIKE Protein Evolved from a PSII Assembly Factor to Mediate Assembly of the Chloroplast NAD(P)H Dehydrogenase Complex in Arabidopsis

In vascular plants, the chloroplast NAD(P)H dehydrogenase complex (NDH-C) is assembled from five distinct subcomplexes, the membrane-spanning (subM) and the luminal (subL) subcomplexes, as well as subA, subB, and subE. The assembly process itself is poorly understood. Vascular plant genomes code for two related intrinsic thylakoid proteins, PHOTOSYNTHESIS-AFFECTED MUTANT68 (PAM68), a photosystem II assembly factor, and PHOTOSYNTHESIS-AFFECTED MUTANT68-LIKE (PAM68L). As we show here, inactivation of Arabidopsis thaliana PAM68L in the pam68l-1 mutant identifies PAM68L as an NDH-C assembly factor. The mutant lacks functional NDH holocomplexes and accumulates three distinct NDH-C assembly intermediates (subB, subM, and subA+L), which are also found in mutants defective in subB assembly (ndf5) or subM expression (CHLORORESPIRATORY REDUCTION4-3 mutant). NDH-C assembly in the cyanobacterium Synechocystis sp PCC 6803 and the moss Physcomitrella patens does not require PAM68 proteins, as demonstrated by the analysis of knockout lines for the single-copy PAM68 genes in these species. We conclude that PAM68L mediates the attachment of subB- and subM-containing intermediates to a complex that contains subA and subL. The evolutionary appearance of subL and PAM68L during the transition from mosses like P. patens to flowering plants suggests that the associated increase in the complexity of the NDH-C might have been facilitated by the recruitment of evolutionarily novel assembly factors like PAM68L