TY - JOUR A1 - Freiberg, Alexander A1 - Baumann, Ingrid A1 - Baumann, Guido T1 - Lipids in callus cultures of sugar beet determined by AMD (automated multiple development) of high-performance thin layer chromatography plates Y1 - 1998 ER - TY - JOUR A1 - Freiberg, Alexander A1 - Morona, Renato A1 - Van den Bosch, Luisa A1 - Jung, Christiane A1 - Behlke, Joachim A1 - Carlin, Nung A1 - Seckler, Robert A1 - Baxa, Ulrich T1 - The tailspike protein of Shigella phage Sf6 : a structural homolog of Salmonella phage P22 tailspike protein without sequence similarity in the beta-helix domain N2 - Bacteriophage Sf6 tailspike protein is functionally equivalent to the well characterized tailspike ofSalmonella phage P22, mediating attachment of the viral particle to host cell-surface polysaccharide. However, there is significant sequence similarity between the two 70-kDa polypeptides only in the N-terminal putative capsid-binding domains. The major, central part of P22 tailspike protein, which forms a parallel ;-helix and is responsible for saccharide binding and hydrolysis, lacks detectable sequence homology to the Sf6 protein. After recombinant expression in Escherichia coli as a soluble protein, the Sf6 protein was purified to homogeneity. As shown by circular dichroism and Fourier transform infrared spectroscopy, the secondary structure contents of Sf6 and P22 tailspike proteins are very similar. Both tailspikes are thermostable homotrimers and resist denaturation by SDS at room temperature. The specific endorhamnosidase activities of Sf6 tailspike protein toward fluorescence-labeled dodeca-, deca-, and octasaccharide fragments of Shigella O-antigen suggest a similar active site topology of both proteins. Upon deletion of the N-terminal putative capsid-binding domain, the protein still forms a thermostable, SDS-resistant trimer that has been crystallized. The observations strongly suggest that the tailspike of phage Sf6 is a trimeric parallel ;-helix protein with high structural similarity to its functional homolog from phage P22. Y1 - 2003 UR - http://www.jbc.org/content/278/3/1542.full SN - 0021-9258 ER - TY - JOUR A1 - Freiberg, Alexander A1 - Machner, M. P. A1 - Pfeil, Wolfgang A1 - Schubert, W. D. A1 - Heinz, Dirk W. A1 - Seckler, Robert T1 - Folding and stability of the leucine-rich repeat domain of internalin B from Listeria monocytogenes N2 - Internalin B (InlB), a surface protein of the human pathogen Listeria monocytogenes, promotes invasion into various host cell types by inducing phagocytosis of the entire bacterium. The N-terminal half of InlB (residues 36-321, InlB(321)), which is sufficient for this process, contains a central leucine-rich repeat (LRR) domain that is flanked by a small a-helical cap 2 and an immunoglobulin (Ig)-like domain. Here we investigated the variant lacking the Ig-like domain (lnlB(248)). The circular dichroism spectra of both protein variants in the far ultraviolet region are very similar, with a characteristic minimum found at similar to200 nm, possibly resulting from the high 3(10)-helical content in the LRR domain. Upon addition of chemical denaturants, both variants unfold in single transitions with unusually high cooperativity that are fully reversible and best described by two-state equilibria. The free energies of GdmCl-induced unfolding determined from transitions at 20degreesC are 9.9(+/- 0.8)kcal/mol for InlB(321) and 5.4(+/- 0.4) kcal/mol for InlB(248). InlB(321) is also more stable against thermal denaturation, as observed by scanning calorimetry. This suggests, that the Ig-like domain, which presumably does not directly interact with the host cell receptor during bacterial invasion, plays a critical role for the in vivo stability of InlB. (C) 2004 Elsevier Ltd. All rights reserved Y1 - 2004 SN - 0022-2836 ER - TY - JOUR A1 - Müller, Jürgen J. A1 - Barbirz, Stefanie A1 - Heinle, Karolin A1 - Freiberg, Alexander A1 - Seckler, Robert A1 - Heinemann, Udo T1 - An intersubunit active site between supercoiled parallel beta helices in the trimeric tailspike endorhamnosidase of Shigella flexneri phage Sf6 N2 - Sf6 belongs to the Podoviridae family of temperate bacteriophages that infect gram-negative bacteria by insertion of their double-stranded DNA. They attach to their hosts specifically via their tailspike proteins. The 1.25 Å crystal structure of Shigella phage Sf6 tailspike protein (Sf6 TSP) reveals a conserved architecture with a central, right-handed ; helix. In the trimer of Sf6 TSP, the parallel ; helices form a left-handed, coiled;; coil with a pitch of 340 Å. The C-terminal domain consists of a ; sandwich reminiscent of viral capsid proteins. Further crystallographic and biochemical analyses show a Shigella cell wall O-antigen fragment to bind to an endorhamnosidase active site located between two ;-helix subunits each anchoring one catalytic carboxylate. The functionally and structurally related bacteriophage, P22 TSP, lacks sequence identity with Sf6 TSP and has its active sites on single subunits. Sf6 TSP may serve as an example for the evolution of different host specificities on a similar general architecture. Y1 - 2008 UR - http://www.cell.com/structure/abstract/S0969-2126%2808%2900106-8 U6 - https://doi.org/10.1016/j.str.2008.01.019 ER - TY - JOUR A1 - Barbirz, Stefanie A1 - Becker, Marion A1 - Freiberg, Alexander A1 - Seckler, Robert T1 - Phage tailspike proteins with beta-solenoid fold as thermostable carbohydrate binding materials N2 - We have investigated the stability of three tailspike proteins (TSPs) from bacteriophages Sf6, P22, and HK620. Tailspikes are rod-like homotrimers with comparable beta-solenoid folds and similarly high kinetic stability in spite of different amino acid sequences. As tailspikes bind polysaccharides to recognize the bacterial host cell, their stability is required for maintenance of bacteriophage infectivity under harsh extracellular conditions. They resist denaturation by SDS at ambient temperature and their unfolding is slow even in 6 m guanidinium hydrochloride (GdmHCl). This makes them interesting candidates for very stable carbohydrate binding protein materials. Y1 - 2009 UR - http://onlinelibrary.wiley.com/journal/10.1002/%28ISSN%291616-5195 U6 - https://doi.org/10.1002/mabi.200800278 SN - 1616-5187 ER -