@article {1350, title = {Single molecule force spectroscopy reveals a weakly populated microstate of the FnIII domains of tenascin}, journal = {Journal of Molecular Biology}, volume = {361}, number = {2}, year = {2006}, note = {ISI Document Delivery No.: 074WPTimes Cited: 8Cited Reference Count: 48Cao, Y. Li, Hongbin}, month = {Aug}, pages = {372-381}, type = {Article}, abstract = {The native states of proteins exist as an ensemble of conformationally similar microstates. The fluctuations among different microstates are of great importance for the functions and structural stability of proteins. Here, we demonstrate that single molecule atomic force microscopy (AFM) can be used to directly probe the existence of multiple folded microstates. We used the AFM to repeatedly stretch and relax a recombinant tenascin fragment TNfnALL to allow the fibronectin type III (FnIII) domains to undergo repeated unfolding/refolding cycles. In addition to the native state, we discovered that some FnIII domains can refold from the unfolded state into a previously unrecognized microstate, N* state. This novel state is conformationally similar to the native state, but mechanically less stable. The native state unfolds at similar to 120 pN, while the N* state unfolds at similar to 50 pN. These two distinct populations of microstates constitute the ensemble of the folded states for some FnIII domains. An unfolded FnIII domain can fold into either one of the two microstates via two distinct folding routes. These results reveal the dynamic and heterogeneous picture of the folded ensemble for some FnIII domains of tenascin, which may carry important implications for the mechanical functions of tenascins in vivo. (c) 2006 Elsevier Ltd. All rights reserved.}, keywords = {DYNAMICS, fluctuations, FnIII domains, HYDROGEN-EXCHANGE, IMMUNOGLOBULIN, MECHANICAL STABILITY, mechanical unfolding, microscopy, MODULES, PROTEIN-STRUCTURE, scanning probe, single-molecule force spectroscopy, tenascin, TITIN, UNFOLDING PATHWAYS}, isbn = {0022-2836}, url = {://000239842800014}, author = {Cao, Y. and Li, H. B.} } @article {1103, title = {Dissecting the domain structure of Cdc4p, a myosin essential light chain involved in Schizosaccharomyces pombe cytokinesis}, journal = {Biochemistry}, volume = {44}, number = {36}, year = {2005}, note = {ISI Document Delivery No.: 962ZGTimes Cited: 3Cited Reference Count: 75}, month = {Sep}, pages = {12136-12148}, type = {Article}, abstract = {Cytokinesis is the process by which one cell divides into two. Key in the cytokinetic mechanism of Schizosaccharomyces pombe is the contractile ring myosin, which consists of two heavy chains (Myo2p), two essential light chains (Cdc4p), and two regulatory light chains (R1c1p). Cdc4p is a dumbbell-shaped EF-hand protein composed of N- and C-terminal domains separated by a flexible linker. The properties of these two domains are of particular interest because each is hypothesized to have independent functions in binding different components of the cytokinesis machinery. To help define these properties, we used NMR spectroscopy to compare the structure, stability, and dynamics of the isolated N- and C-terminal domains with one another and with native Cdc4p. On the basis of invariant chemical shifts, the N-domain retains the same structure in isolation as in the context of the full-length Cdc4p, whereas the C-domain appears markedly perturbed. This perturbation results from intramolecular binding of the residual linker sequence at the N-terminus of the C-domain in a mode similar to that used by native Cdc4p to associate with target polypeptide sequences. NMR relaxation, thermal denaturation, and amide hydrogen exchange experiments also indicate that the C-domain is less stable and more dynamic than the N-domain, both in isolation and in the full-length protein. We hypothesize that these properties reflect a conformational plasticity of the C-domain, which may allow Cdc4p to interact with several regulatory or contractile ring proteins necessary for cytokinesis.}, keywords = {CALCIUM-MODULATED PROTEINS, CONFORMATIONAL CHANGE, CONTRACTILE RING, FISSION, GROUP, HYDROGEN-EXCHANGE, MUSCLE TROPONIN-C, N-15 NMR RELAXATION, NUCLEAR MAGNETIC-RESONANCE, SACCHAROMYCES-CEREVISIAE, SKELETAL-MUSCLE, YEAST}, isbn = {0006-2960}, url = {://000231771500022}, author = {Escobar-Cabrera, E. and Venkatesan, M. and Desautels, M. and Hemmingsen, S. M. and McIntosh, L. P.} } @article {4617, title = {Cavitands are effective templates for inducing stability and nativelike structure in de Novo four-helix bundles}, journal = {Journal of the American Chemical Society}, volume = {121}, number = {39}, year = {1999}, note = {ISI Document Delivery No.: 243QXTimes Cited: 40Cited Reference Count: 92}, month = {Oct}, pages = {8983-8994}, type = {Article}, abstract = {We have designed, synthesized and characterized eight cavitand-based de novo four-helix bundles, where each helix contains the basis sequence EELLKKLEELLKKG. We find that each de novo protein is highly helical and extremely stable to the chemical denaturant guanidine hydrochloride (GuHCl). We studied the effect of the cavitand-peptide linker on the stability of each de novo protein. Flexible linkers render the helical structures more susceptible to denaturation by GuHCl. Linker structure and length also dictate monomer/dimer equilibria of the proteins. Proteins containing 0-3 Cry units possess varying degrees of nativelike structure. In contrast, proteins containing two or four methylene Linkers are more characteristic of molten globules. These differences can be attributed to the additional hydrogen bonding capabilities of the glycine linker variants and to the distance between the cavitand template and the helical bundle. The cavitand pendent group was also changed in one de novo protein from a methyl group to a propyl-phosphate moiety. This alteration does not affect the stability or packing within the helical bundle; however, it does affect the monomer/dimer equilibrium.}, keywords = {4-HELIX BUNDLE, ASSEMBLED, conformational, DESIGNED PROTEIN, HOST GUEST COMPLEXATION, HYDROGEN-EXCHANGE, MOLTEN GLOBULE, NONPOLAR AMINO-ACIDS, rational design, STABILITY, SYNTHETIC PROTEINS, ULTRAVIOLET CIRCULAR-DICHROISM}, isbn = {0002-7863}, url = {://000083009700003}, author = {Mezo, A. R. and Sherman, J. C.} }