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1.  Functional demonstrations of starch binding domains present in Ostreococcus tauri starch synthases isoforms 
BMC Research Notes  2015;8:613.
Starch-binding domains are key modules present in several enzymes involved in polysaccharide metabolism. These non-catalytic modules have already been described as essential for starch-binding and the catalytic activity of starch synthase III from the higher plant Arabidopsis thaliana. In Ostreococcus tauri, a unicellular green alga of the Prasinophyceae family, there are three SSIII isoforms, known as Ostta SSIII-A, SSIII-B and SSIII-C.
In this work, using in silico and in vitro characterization techniques, we have demonstrated that Ostta SSIII-A, SSIII-B and SSIII-C contain two, three and no starch-binding domains, respectively. Additionally, our phylogenetic analysis has indicated that OsttaSSIII-B, presenting three N-terminal SBDs, is the isoform more closely related to higher plant SSIII. Furthermore, the sequence alignment and homology modeling data gathered showed that both the main 3-D structures of all the modeled domains obtained and the main amino acid residues implicated in starch binding are well conserved in O. tauri SSIII starch-binding domains. In addition, adsorption assays showed that OsttaSSIII-A D2 and SSIII-B D2 domains are the two that make the greatest contribution to amylose and amylopectin binding, while OsttaSSIII-B D1 is also important for starch binding.
The results presented here suggest that differences between OsttaSSIII-A and SSIII-B SBDs in the number of and binding of amino acid residues may produce differential affinities for each isoform to polysaccharides. Increasing the knowledge about SBDs may lead to their employment in biomedical and industrial applications.
Electronic supplementary material
The online version of this article (doi:10.1186/s13104-015-1598-6) contains supplementary material, which is available to authorized users.
PMCID: PMC4625611  PMID: 26510916
Ostreococcus tauri; Starch-binding domains; Starch synthase; Homology modeling; Adsorption assay
2.  The PhoP/PhoQ System and Its Role in Serratia marcescens Pathogenesis 
Journal of Bacteriology  2012;194(11):2949-2961.
Serratia marcescens is able to invade, persist, and multiply inside nonphagocytic cells, residing in nonacidic, nondegradative, autophagosome-like vacuoles. In this work, we have examined the physiological role of the PhoP/PhoQ system and its function in the control of critical virulence phenotypes in S. marcescens. We have demonstrated the involvement of the PhoP/PhoQ system in the adaptation of this bacterium to growth on scarce environmental Mg2+, at acidic pH, and in the presence of polymyxin B. We have also shown that these environmental conditions constitute signals that activate the PhoP/PhoQ system. We have found that the two S. marcescens mgtE orthologs present a conserved PhoP-binding motif and demonstrated that mgtE1 expression is PhoP dependent, reinforcing the importance of PhoP control in magnesium homeostasis. Finally, we have demonstrated that phoP expression is activated intracellularly and that a phoP mutant strain is defective in survival inside epithelial cells. We have shown that the Serratia PhoP/PhoQ system is involved in prevention of the delivery to degradative/acidic compartments.
PMCID: PMC3370626  PMID: 22467788
3.  mgtA Expression Is Induced by Rob Overexpression and Mediates a Salmonella enterica Resistance Phenotype▿  
Journal of Bacteriology  2008;190(14):4951-4958.
Rob is a member of the Sox/Mar subfamily of AraC/XylS-type transcriptional regulators implicated in bacterial multidrug, heavy metal, superoxide, and organic solvent resistance phenotypes. We demonstrate that, in Salmonella enterica, Rob overexpression upregulates the transcription of mgtA, which codes for the MgtA Mg2+ transporter. mgtA was previously characterized as a member of the Mg2+-modulated PhoPQ regulon. Here we demonstrate that Rob (but not its paralog protein SoxS or MarA) is able to induce mgtA transcription in a PhoP-independent fashion by binding to a conserved Mar/Sox/Rob motif localized downstream of the PhoP-box and overlapping the PhoP-dependent transcriptional start site. We found that Rob-induced mgtA expression confers low-level cyclohexane resistance on Salmonella. Because mgtA intactness is required for Rob-induced cyclohexane resistance, provided the AcrAB multidrug efflux pump can be expressed, we postulate that MgtA is involved in the AcrAB-mediated cyclohexane detoxification mechanism promoted by Rob in Salmonella.
PMCID: PMC2447000  PMID: 18487336

Results 1-3 (3)