Exceptional Uptake, Limited Protein Expression: Liver Macrophages Lost in Translation of Synthetic mRNA.

Most gene therapies exert their actions via manipulation of hepatocytes (parenchymal cells) and the reasons behind the suboptimal performance of synthetic mRNA in non-parenchymal cells (NPC) such as Kupffer cells (KC), and liver macrophages, remain unclear. Here, the spatio-temporal distribution of mRNA encoding enhanced green fluorescent protein (Egfp), siRNA, or both co-encapsulated into lipid nanoparticles (LNP) in the liver in vivo using real-time intravital imaging is investigated. Although both KC and hepatocytes demonstrate comparable high and rapid uptake of mRNA-LNP and siRNA-LNP in vivo, the translation of Egfp mRNA occurs exclusively in hepatocytes during intravital imaging.

Binding and reduction of sulfite by cytochrome c nitrite reductase.

Pentaheme cytochrome c nitrite reductase (ccNiR) catalyzes the six-electron reduction of nitrite to ammonia as the final step in the dissimilatory pathway of nitrate ammonification. It has also been shown to reduce sulfite to sulfide, thus forming the only known link between the biogeochemical cycles of nitrogen and of sulfur. We have found the sulfite reductase activity of ccNiR from Wolinella succinogenes to be significantly smaller than its nitrite reductase activity but still several times higher than the one described for dissimilatory, siroheme-containing sulfite reductases.

Crystallization and preliminary X-ray analysis of the membrane-bound cytochrome c nitrite reductase complex (NrfHA) from Wolinella succinogenes.

Crystals of the complex between the enzyme cytochrome c nitrite reductase (NrfA) and the membrane-bound quinol oxidase and electron carrier NrfH were grown by vapour diffusion using ammonium sulfate as a precipitant. In the epsilon-proteobacterium Wolinella succinogenes, NrfA and NrfH form a functional membrane-bound complex which catalyzes the last step in the metabolic pathway of nitrate dissimilation. NrfH represents a prototype of a large family of putative bacterial quinol oxidases, the NapC/NirT family, which have been proposed to serve as electron donors for a variety of reductases.