@article{AndresBaxaHankeetal.2010,
  author    = {Andres, Dorothee and Baxa, Ulrich and Hanke, Christin and Seckler, Robert and Barbirz, Stefanie},
  title     = {Carbohydrate binding of Salmonella phage P22 tailspike protein and its role during host cell infection},
  issn      = {0300-5127},
  doi       = {10.1042/Bst0381386},
  year      = {2010},
  abstract  = {TSPs (tailspike proteins) are essential infection organelles of bacteriophage P22. Upon infection, P22TSP binds to and cleaves the O-antigen moiety of the LPS (lipopolysaccharide) of its Salmonella host To elucidate the role of TSP during infection, we have studied binding to oligosaccharides and polysaccharides of Salmonella enteric Typhimurium and Enteritidis in vitro. P22TSP is a trimeric beta-helical protein with a carbohydrate-binding site on each subunit. Octasaccharide O-antigen fragments bind to P22TSP with micromolar dissociation constants. Moreover, P22TSP is an endorhamnosidase and cleaves the host O-antigen. Catalytic residues lie at the periphery of the high-affinity binding site, which enables unproductive binding modes, resulting in slow hydrolysis. However, the role of this hydrolysis function during infection remains unclear. Binding of polysaccharide to P22TSP is of high avidity with slow dissociation rates when compared with oligosaccharides. In vivo, the infection of Salmonella with phage P22 can be completely inhibited by the addition of LPS, indicating that binding of phage to its host via TSP is an essential step for infection.},
  language  = {en}
}
@article{AndresHankeBaxaetal.2010,
  author    = {Andres, Dorothee and Hanke, Christin and Baxa, Ulrich and Seul, Anait and Barbirz, Stefanie and Seckler, Robert},
  title     = {Tailspike interactions with lipopolysaccharide effect DNA ejection from phage P22 particles in vitro},
  issn      = {0021-9258},
  doi       = {10.1074/jbc.M110.169003},
  year      = {2010},
  abstract  = {Initial attachment of bacteriophage P22 to the Salmonella host cell is known to be mediated by interactions between lipopolysaccharide (LPS) and the phage tailspike proteins (TSP), but the events that subsequently lead to DNA injection into the bacterium are unknown. We used the binding of a fluorescent dye and DNA accessibility to DNase and restriction enzymes to analyze DNA ejection from phage particles in vitro. Ejection was specifically triggered by aggregates of purified Salmonella LPS but not by LPS with different O-antigen structure, by lipid A, phospholipids, or soluble O-antigen polysaccharide. This suggests that P22 does not use a secondary receptor at the bacterial outer membrane surface. Using phage particles reconstituted with purified mutant TSP in vitro, we found that the endorhamnosidase activity of TSP degrading the O-antigen polysaccharide was required prior to DNA ejection in vitro and DNA replication in vivo. If, however, LPS was pre-digested with soluble TSP, it was no longer able to trigger DNA ejection, even though it still contained five O-antigen oligosaccharide repeats. Together with known data on the structure of LPS and phage P22, our results suggest a molecular model. In this model, tail-spikes position the phage particles on the outer membrane surface for DNA ejection. They force gp26, the central needle and plug protein of the phage tail machine, through the core oligosaccharide layer and into the hydrophobic portion of the outer membrane, leading to refolding of the gp26 lazo-domain, release of the plug, and ejection of DNA and pilot proteins.},
  language  = {en}
}
@article{ThalhammerHundertmarkPopovaetal.2010,
  author    = {Thalhammer, Anja and Hundertmark, Michaela and Popova, Antoaneta V. and Seckler, Robert and Hincha, Dirk K.},
  title     = {Interaction of two intrinsically disordered plant stress proteins (COR15A and COR15B) with lipid membranes in the dry state},
  issn      = {0005-2736},
  doi       = {10.1016/j.bbamem.2010.05.015},
  year      = {2010},
  abstract  = {COR15A and COR15B form a tandem repeat of highly homologous genes in Arabidopsis thaliana. Both genes are highly cold induced and the encoded proteins belong to the Pfam LEA_4 group (group 3) of the late embryogenesis abundant (LEA) proteins. Both proteins were predicted to be intrinsically disordered in solution. Only COR15A has previously been characterized and it was shown to be localized in the soluble stroma fraction of chloroplasts. Ectopic expression of COR15A in Arabidopsis resulted in increased freezing tolerance of both chloroplasts after freezing and thawing of intact leaves and of isolated protoplasts frozen and thawed in vitro. In the present study we have generated recombinant mature COR15A and COR15B for a comparative study of their structure and possible function as membrane protectants. CD spectroscopy showed that both proteins are predominantly unstructured in solution and mainly a-helical after drying. Both proteins showed similar effects on the thermotropic phase behavior of dry liposomes. A decrease in the gel to liquid-crystalline phase transition temperature depended on both the unsaturation of the fatty acyl chains and lipid headgroup structure. FTIR spectroscopy indicated no strong interactions between the proteins and the lipid phosphate and carbonyl groups, but significant interactions with the galactose headgroup of the chloroplast lipid monogalactosyldiacylglycerol. These findings were rationalized by modeling the secondary structure of COR15A and COR15B. Helical wheel projection indicated the presence of amphipathic a-helices in both proteins. The helices lacked a clear separation of positive and negative charges on the hydrophilic face, but contained several hydroxylated amino acids.},
  language  = {en}
}