Context-dependent effects of charged residues in transmembrane segments of MalF–PhoA fusions

Ehrle, Rainer; Mikhaleva, Natasha; Boyd, Dana; Davidson, Amy L.; Ehrmann, Michael

doi:10.1016/j.resmic.2003.07.001

Cited by 2 publications

(1 citation statement)

References 26 publications

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“…In contrast, the ExoIII fusion at S89 within the same predicted loop, had negligible AP activity. Four positively charged residues (K and R) are present between Wzx residues E75 and S89, that are involved in stopping transfer through the inner membrane of newly synthesized proteins and are cytoplasmic loop determinants (Ehrle et al , 2003). The absence of these residues in the E75 fusion may have resulted in the upstream region not being anchored within the cytoplasm and with the extra eight codons present at the fusion junction in ExoIII‐derived constructs, but not site‐specific ones, may have allowed the PhoA fragment to span and clear the inner membrane to the periplasm and account for the activity observed.…”

Section: Resultsmentioning

confidence: 99%

Membrane topology of theSalmonella entericaserovar Typhimurium Group B O-antigen translocase Wzx

Cunneen

Reeves

2008

FEMS Microbiology Letters

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The O-antigen translocase, Wzx, is involved in translocation of bacterial polysaccharide repeat units across the cytoplasmic membrane, and is an unusually diverse, highly hydrophobic protein, with high numbers of predicted alpha-helical transmembrane segments (TMS). The Salmonella enterica serovar Typhimurium Group B O-antigen Wzx was an ideal candidate for topological study as the O-antigen gene cluster is one of only a few that have been well characterized. The topology profile prediction for this protein was determined using five programs, with different recognition parameters, which consistently predict that 12 TMS are present. A membrane topology model was constructed by analysis of lacZ and phoA gene fusions at randomly selected and targeted fusion sites within wzx. Enzyme activity of these, and full-length C-terminal fusion proteins, confirmed the 12-TMS topology for this Wzx, and also indicated that the C-terminus was located within the cytoplasm, which is consistent with the predicted topology.

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Section: Resultsmentioning

confidence: 99%

Membrane topology of theSalmonella entericaserovar Typhimurium Group B O-antigen translocase Wzx

Cunneen

Reeves

2008

FEMS Microbiology Letters

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Topological and transcriptional analysis of pssL gene product: a putative Wzx-like exopolysaccharide translocase in Rhizobium leguminosarum bv. trifolii TA1

et al. 2005

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An identified pssL gene is yet another one, besides the pssT, pssN and pssP genes, encoding for a protein engaged in polysaccharide polymerization and export in Rhizobium leguminosarum bv. trifolii strain TA1 (RtTA1). Amino acid sequence similarity and hypothetical protein secondary structure placed the PssL protein within Wzx (RfbX) translocases with putative flippase function that belong to the polysaccharide specific transport (PST) family. The predicted secondary structure of the PssL membrane protein was examined with a series of PssL-PhoA and PssL-LacZ translational fusions. The results support the hypothesis of PssL being a member of PST protein family comprising transporters with 12 membrane spanning segments and amino and carboxyl termini located in the cytoplasm. Results of semi-quantitative RT-PCR showed that the initial abundance of mRNA encoding PssL protein was relatively lower when compared to the quantity of the previously identified PssT membrane protein. PssL might be a good candidate for Wzx-like protein that together with PssT (Wzy protein) could be responsible for Wzx/Wzy-like-dependent EPS polymerization and translocation in RtTA1.

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Context-dependent effects of charged residues in transmembrane segments of MalF–PhoA fusions

Cited by 2 publications

References 26 publications

Membrane topology of theSalmonella entericaserovar Typhimurium Group B O-antigen translocase Wzx

Membrane topology of theSalmonella entericaserovar Typhimurium Group B O-antigen translocase Wzx

Topological and transcriptional analysis of pssL gene product: a putative Wzx-like exopolysaccharide translocase in Rhizobium leguminosarum bv. trifolii TA1

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