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The mechanisms controlling membrane recognition by proteins with one hydrophobic stretch at their carboxyl terminus (tail anchor, TA) are poorly defined. The Escherichia coli TAs of ElaB and YqjD, which share sequential and structural similarity with the Saccharomyces cerevisiae TA of Fis1, were shown to localize to mitochondria. We show that YqjD and ElaB are directed by their TAs to bacterial cell poles. Fis1(TA) expressed in E. coli localizes like the endogenous TAs. The yeast and bacterial TAs are inserted in the E. coli inner membrane, and they all show affiliation to phosphatidic acid (PA), found in the membrane of the bacterial cell poles and of the yeast mitochondria. Our results suggest a mechanism for TA membrane recognition conserved from bacteria to mitochondria and raise the possibility that through their interaction with PA, and TAs play a role across prokaryotes and eukaryotes in controlling cell/organelle fate. [ABSTRACT FROM AUTHOR]

Parathyroid hormone‐related protein (PTHrP) is transported to both the secretory pathway and the nucleus/nucleolus by its dual targeting signals, that is, an N‐terminal signal peptide and nuclear targeting signal. Curiously, reporter proteins such as enhanced green fluorescent protein strongly affect the localization of the fusion protein. Here, we report a novel methionine tag for 35S‐labelling added to the C‐terminus of its prepro‐form, which has no methionine and cysteine residue other than the initiation methionine that enables analyses of the molecular mechanism of its dual localization without the effects of the reporter proteins. Mutational analyses including insertion of a glycosylation site for the tagged PTHrP revealed that the evolutionarily conserved regions in the signal peptide and the pro‐region facilitate the redirection of ppPTHrP from the secretory pathway to the nuclear targeting pathway. [ABSTRACT FROM AUTHOR]

Abstract: MIZ1 is encoded by a gene essential for root hydrotropism in Arabidopsis. To characterize the property of MIZ1, we used transgenic plants expressing GFP-tagged MIZ1 (MIZ1-GFP) and mutant MIZ1 (MIZ1G235E-GFP) in a miz1-1 mutant. Although both chimeric genes were transcribed, the translational products of MIZ1G235E-GFP did not accumulate in roots. Moreover, MIZ1-GFP complemented the mutant phenotype but not MIZ1G235E-GFP. The signal corresponding to MIZ1-GFP was detected at high levels in cortical cells and lateral root cap cells and accumulated in compartments in cortical cells. MIZ1-GFP was fractionated into a soluble protein fraction and an endoplasmic reticulum (ER) membrane fraction, where it was bound to the surface of the ER membrane at the cytosolic side. [Copyright &y& Elsevier]

Abstract: Complex I (NADH:ubiquinone oxidoreductase) is the first and largest protein complex of the oxidative phosphorylation. Crystal structures have elucidated the positions of most subunits of bacterial evolutionary origin in the complex, but the positions of the eukaryotic subunits are unknown. Based on the analysis of sequence conservation we propose intra-molecular disulfide bridges and the inter-membrane space localization of three Cx9C-containing subunits in human: NDUFS5, NDUFB7 and NDUFA8. We experimentally confirm the localization of the latter two, while our data are consistent with disulfide bridges in NDUFA8. We propose these subunits stabilize the membrane domain of complex I. Structured summary: NDUFA8 and NDUFS3 physically interact by blue native page (View interaction) [Copyright &y& Elsevier]

Abstract: Occludin is an integral-membrane protein that contributes to tight junction function. We have identified casein kinase Iε (CKIε) as a binding partner for the C-terminal cytoplasmic domain of occludin by yeast two-hybrid screening. CKIε phosphorylated occludin and co-localised and co-immunoprecipitated with occludin from human endothelial cells. Amino acids 265–318 of occludin were sufficient for CKIε binding and phosphorylation. Deletion of the C-terminal 48 amino acids of occludin increased CKIε binding and phosphorylation, suggesting that this region inhibits CKIε binding. These data identify CKIε as a novel occludin kinase that may be important for the regulation of occludin. [Copyright &y& Elsevier]