Dual topology of the Escherichia coli TatA protein.

The Escherichia coli Tat system has unusual capacity of translocating folded proteins across the cytoplasmic membrane. The TatA protein is the most abundant known Tat component and consists of a transmembrane segment followed by an amphipathic helix and a hydrophilic C terminus. To study the operation mechanism of the Tat apparatus, we analyzed the topology of TatA.

Glucose 6-phosphate dehydrogenase is required for sucrose and trehalose to be efficient osmoprotectants in Sinorhizobium meliloti.

Inactivation of the zwf gene in Sinorhizobium meliloti induces an osmosensitive phenotype and the loss of osmoprotection by trehalose and sucrose, but not by ectoine and glycine betaine. This phenotype is not linked to a defect in the biosynthesis of endogenous solutes. zwf expression is induced by high osmolarity, sucrose and trehalose, but is repressed by betaine.

In vivo interaction between the polyprenol phosphate mannose synthase Ppm1 and the integral membrane protein Ppm2 from Mycobacterium smegmatis revealed by a bacterial two-hybrid system.

Dolichol phosphate-mannose (Dol-P-Man) is a mannose donor in various eukaryotic glycosylation processes. So far, two groups of Dol-P-Man synthases have been characterized based on the way they are stabilized in the endoplasmic reticulum membrane. Enzymes belonging to the first group, such as the yeast Dpm1, are typical integral membrane proteins harboring a transmembrane segment (TMS) at their C terminus.

Topology determination and functional analysis of the Escherichia coli TatC protein.

The TatC protein is an essential component of the bacterial Tat system. By using alkaline phosphatase and beta-glucuronidase fusions we found that TatC contains four transmembrane helices. Three insertions of Ala-Ser dipeptide at the cytoplasmic N- and C-termini and in the cytoplasmic loop had no or only partial effect on the TatC function.