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Secretion Pathway (secretion + pathway)
Selected AbstractsBiogenesis of Yersinia pestis PsaA in recombinant attenuated Salmonella Typhimurium vaccine (RASV) strainFEMS MICROBIOLOGY LETTERS, Issue 2 2010Ascención Torres-Escobar Abstract Yersinia pestis PsaA is an adhesin important for the establishment of bacterial infection. PsaA synthesis requires the products of the psaEFABC genes. Here, by prediction analysis, we identified a PsaA signal sequence with two signal peptidase (SPase) cleavage sites, type-I and type-II (SPase-I and SPase-II). By Edman degradation and site-directed mutagenesis, the precise site for one of these Spase-I PsaA cleavage sites was located between alanine and serine at positions 31 and 32, respectively. Yersinia pestis psaA expression and the role of the PsaB and PsaC proteins were evaluated in recombinant attenuated Salmonella Typhimurium vaccine strains. PsaA was detected in total extracts as a major 15-kDa (mature) and 18-kDa (unprocessed) protein bands. PsaA synthesis was not altered by a ,A31,,S32 double-deletion mutation. In contrast, the synthesis of PsaA (,A31,,S32) in Y. pestis and delivery to the supernatant was decreased. Otherwise, substitution of the amino acid cysteine at position 26 by valine involved in the SPase-II cleavage site did not show any effect on the secretion of PsaA in Salmonella and Yersinia. These results help clarify the secretion pathway of PsaA for the possible development of vaccines against Y. pestis. [source] Stereoselective renal tubular secretion of levocetirizine and dextrocetirizine, the two enantiomers of the H1 -antihistamine cetirizineFUNDAMENTAL & CLINICAL PHARMACOLOGY, Issue 1 2008M. Strolin Benedetti Abstract Competition for uptake and/or efflux transporters can be responsible for drug interactions. Cetirizine is mainly eliminated unchanged in urine through both glomerular filtration and tubular secretion. The aim of this study was to investigate whether the eutomer, levocetirizine, and the distomer, dextrocetirizine, have a similar tubular secretion. The renal clearance associated with tubular secretion was calculated from the renal clearance of levocetirizine and dextrocetirizine obtained in a study in healthy volunteers. The values of the unbound fraction in plasma were obtained in an in vitro study of the binding of 14C-cetirizine and 14C-levocetirizine to human plasma proteins using equilibrium dialysis and chiral high-performance liquid chromatography (HPLC) with on-line liquid scintillation counting. The unbound fraction was 0.074 for levocetirizine and 0.141 for dextrocetirizine. The tubular secretion of dextrocetirizine (44.5 mL/min) is higher than that of levocetirizine (23.1 mL/min), which may have consequences for drug interactions at the renal level. The higher tubular secretion for dextrocetirizine may be due to the higher free fraction available for secretion or to a higher affinity for (a) renal transporter(s) mediating the secretion pathway. [source] Exploration of twin-arginine translocation for expression and purification of correctly folded proteins in Escherichia coliMICROBIAL BIOTECHNOLOGY, Issue 5 2008Adam C. Fisher Summary Historically, the general secretory (Sec) pathway of Gram-negative bacteria has served as the primary route by which heterologous proteins are delivered to the periplasm in numerous expression and engineering applications. Here we have systematically examined the twin-arginine translocation (Tat) pathway as an alternative, and possibly advantageous, secretion pathway for heterologous proteins. Overall, we found that: (i) export efficiency and periplasmic yield of a model substrate were affected by the composition of the Tat signal peptide, (ii) Tat substrates were correctly processed at their N-termini upon reaching the periplasm and (iii) proteins fused to maltose-binding protein (MBP) were reliably exported by the Tat system, but only when correctly folded; aberrantly folded MBP fusions were excluded by the Tat pathway's folding quality control feature. We also observed that Tat export yield was comparable to Sec for relatively small, well-folded proteins, higher relative to Sec for proteins that required cytoplasmic folding, and lower relative to Sec for larger, soluble fusion proteins. Interestingly, the specific activity of material purified from the periplasm was higher for certain Tat substrates relative to their Sec counterparts, suggesting that Tat expression can give rise to relatively pure and highly active proteins in one step. [source] Analysis of the requirements for pilus biogenesis at the outer membrane usher and the function of the usher C-terminusMOLECULAR MICROBIOLOGY, Issue 2 2006Stephane Shu Kin So Summary Uropathogenic strains of Escherichia coli assemble type 1 and P pili to colonize the bladder and kidney respectively. These pili are prototype structures assembled by the chaperone/usher secretion pathway. In this pathway, a periplasmic chaperone works together with an outer membrane (OM) usher to control the folding of pilus subunits, their assembly into a pilus fibre and secretion of the fibre to the cell surface. The usher serves as the assembly and secretion platform in the OM. The usher has distinct functional domains, with the N-terminus providing the initial targeting site for chaperone,subunit complexes and the C-terminus required for subsequent stages of pilus biogenesis. In this study, we investigated the molecular interactions occurring at the usher during pilus biogenesis and the function of the usher C-terminus. We provide genetic and biochemical evidence that the usher functions as a complex in the OM and that interaction of the pilus adhesin with the usher is critical to prime the usher for pilus biogenesis. Analysis of C-terminal truncation and substitution mutants of the P pilus usher PapC demonstrated that the C-terminus is required for proper binding of chaperone,subunit complexes to the usher and plays an important role in assembly of complete pili. [source] Chaperones of the type III secretion pathway: jacks of all tradesMOLECULAR MICROBIOLOGY, Issue 1 2002Anne-Laure Page Summary The type III secretion (TTS) pathway is used by many Gram-negative bacteria to inject virulence proteins into cells of their host. The activity of the TTS apparatus is controlled by external signals and, in certain conditions, production and secretion are not coupled. Storage of some proteins before secretion involves their association with specific chaperones. Three classes of TTS chaperones have been distinguished according to whether they associate with: (i) one; (ii) several effector proteins; or (iii) the two translocators that allow passage of effectors across the membrane of eukaryotic cells. These chaperones are required for stabilization of their substrate(s) and prevention of their premature interactions with other partners during storage. They also play a role in secretion of their substrate(s). Some chaperones are also involved in transcriptional regulation of certain genes in response to the activity of secretion. The flagellar export apparatus is closely related to the TTS apparatus and some proteins of the flagellar export system have also been proposed to be chaperones that prevent premature interactions between the flagellum subunits. [source] Crystallographic characterization of the passenger domain of the Bordetella autotransporter BrkAACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 6 2009Li Zhao Autotransporters (ATs) are proteins that deliver effectors (the passenger domain) to the surface of Gram-negative bacteria by the type V secretion pathway. The passenger domain of BrkA, a Bordetella pertussis autotransporter mediating serum resistance and adherence, was cloned in a pET expression system and overexpressed in Escherichia coli. The gene product was correctly refolded, purified to homogeneity and crystallized. The crystals diffracted to 2.8,Å resolution. The space group was assumed to be P41212, with unit-cell parameters a = b = 108.19, c = 115.35,Å. [source] Protein secretion systems in MycobacteriaCELLULAR MICROBIOLOGY, Issue 6 2007Patricia A. DiGiuseppe Champion Summary Mycobacteria have a unique cell-envelope structure which protects the bacteria from the extracellular environment by limiting access to noxious molecules from the outside. This extremely hydrophobic and thick barrier also poses a unique problem for the export of bacterial products. Here we review the multiple protein secretion pathways in Mycobacteria, including the general secretion pathway and the Twin-Arginine Transporter, with an emphasis on the ESX-1 alternate secretion system. This newly identified protein secretion system is required for growth during infection and has provided insight into how M. tuberculosis manipulates the host immune response during infection. [source] | ||||||||||