@article {2072, title = {Phage display and crystallographic analysis reveals potential substrate/binding site interactions in the protein secretion chaperone CsaA from Agrobacterium tumefaciens}, journal = {Journal of Molecular Biology}, volume = {379}, number = {3}, year = {2008}, note = {ISI Document Delivery No.: 311FQTimes Cited: 0Cited Reference Count: 52Feldman, Anat R. Shapova, Yuliya A. Wu, Sampson S. T. Oliver, David C. Heller, Markus McIntosh, Lawrence P. Scott, Jamie K. Paetzel, Mark}, month = {Jun}, pages = {457-470}, type = {Article}, abstract = {The protein CsaA has been proposed to function as a protein secretion chaperone in bacteria that lack the Sec-dependent protein-targeting chaperone SecB. CsaA is a homodimer with two putative substrate-binding pockets, one in each monomer. To test the hypothesis that these cavities are indeed substrate-binding sites able to interact with other polypeptide chains, we selected a peptide that bound to CsaA from a random peptide library displayed on phage. Presented here is the structure of CsaA from Agrobacterium tumefaciens (AtCsaA) solved in the presence and absence of the selected peptide. To promote co-crystallization, the sequence for this peptide was genetically fused to the amino-terminus of AtCsaA. The resulting 1.65 angstrom resolution crystal structure reveals that the tethered peptide from one AtCsaA molecule binds to the proposed substrate-binding pocket of a symmetry-related molecule possibly mimicking the interaction between a pre-protein substrate and CsaA. The structure shows that the peptide lies in an extended conformation with alanine, proline and glutamine side chains pointing into the binding pocket. The peptide interacts with the atoms of the AtCsaA-binding pocket via seven direct hydrogen bonds. The side chain of a conserved pocket residue, Arg76, has an "up" conformation when the CsaA-binding site is empty and a "down" conformation when the CsaA-binding site is occupied, suggesting that this residue may function to stabilize the peptide in the binding cavity. The presented aggregation assays, phage-display analysis and structural analysis are consistent with AtCsaA being a general chaperone. The properties of the proposed CsaA-binding pocket/peptide interactions are compared to those from other structurally characterized molecular chaperones. (c) 2008 Elsevier Ltd. All rights reserved.}, keywords = {BACILLUS-SUBTILIS CSAA, BACTERIAL SIGNAL PEPTIDASE, BINDING PROTEIN, CHANNEL, CRYSTAL-STRUCTURE, CsaA, DISPLAY, LIBRARIES, molecular chaperone, phage, PROTEIN SECRETION, protein targeting, SECA, SEQUENCE, STRUCTURAL SUPERPOSITION, TRANSLOCATION}, isbn = {0022-2836}, url = {://000256586500006}, author = {Feldman, A. R. and Shapova, Y. A. and Wu, S. S. T. and Oliver, D. C. and Heller, M. and McIntosh, L. P. and Scott, J. K. and Paetzel, M.} } @article {1163, title = {First passage times of driven DNA hairpin unzipping}, journal = {Physical Biology}, volume = {2}, number = {3}, year = {2005}, note = {ISI Document Delivery No.: 007TLTimes Cited: 11Cited Reference Count: 25}, month = {Sep}, pages = {166-174}, type = {Article}, abstract = {We model the dynamics of voltage-driven transport of DNA hairpins through transmembrane channels. A two-dimensional stochastic model of the DNA translocation process is fit to the measurements of Mathe, who pulled self-hybridized DNA hairpins through lipid-embedded alpha-hemolysin channels. As the channel was too narrow to accommodate hybridized DNA, dehybridization of the hairpin became the rate-limiting step of the transport process. We show that the mean first passage time versus voltage curve for the escape of the DNA from the transmembrane channel can be divided into two regions: (1) a low-voltage region where the DNA slides out of the pore in reverse and without undergoing significant dehybridization, and (2) a region where the DNA dehybridizes under the influence of the applied voltage and translocates across the membrane.}, keywords = {CHANNEL, DYNAMICS, FORCE, MEMBRANE, MOLECULES, NANOPORE, POLYMER TRANSLOCATION, PORE, SEQUENCE}, isbn = {1478-3967}, url = {://000234992600006}, author = {Lakatos, G. and Chou, T. and Bergersen, B. and Patey, G. N.} } @article {3343, title = {PROTOTYPE FOR A NEW FAMILY OF DE-NOVO PROTEINS}, journal = {Tetrahedron Letters}, volume = {36}, number = {42}, year = {1995}, note = {ISI Document Delivery No.: RZ295Times Cited: 24Cited Reference Count: 30}, month = {Oct}, pages = {7587-7590}, type = {Article}, abstract = {We report the design, synthesis, and preliminary structural analysis of a four-helix bundle affixed to a rigid organic macrocycle.}, keywords = {ASSEMBLED SYNTHETIC PROTEINS, CAVITANDS, CHANNEL, DESIGN, HOST GUEST COMPLEXATION, MOLECULAR, PEPTIDE, TASP, TOPOLOGY, VESSELS}, isbn = {0040-4039}, url = {://A1995RZ29500004}, author = {Gibb, B. C. and Mezo, A. R. and Sherman, J. C.} }