@article {2653,
	title = {Helix Straightening as an Activation Mechanism in the Gelsolin Superfamily of Actin Regulatory Proteins},
	journal = {Journal of Biological Chemistry},
	volume = {284},
	number = {32},
	year = {2009},
	note = {ISI Document Delivery No.: 478CCTimes Cited: 4Cited Reference Count: 23Wang, Hui Chumnarnsilpa, Sakesit Loonchanta, Anantasak Li, Qiang Kuan, Yang-Mei Robine, Sylvie Larsson, Marten Mihalek, Ivana Burtnick, Leslie D. Robinson, Robert C.},
	month = {Aug},
	pages = {21265-21269},
	type = {Article},
	abstract = {Villin and gelsolin consist of six homologous domains of the gelsolin/cofilin fold (V1-V6 and G1-G6, respectively). Villin differs from gelsolin in possessing at its C terminus an unrelated seventh domain, the villin headpiece. Here, we present the crystal structure of villin domain V6 in an environment in which intact villin would be inactive, in the absence of bound Ca2+ or phosphorylation. The structure of V6 more closely resembles that of the activated form of G6, which contains one bound Ca2+, rather than that of the calcium ion-free form of G6 within intact inactive gelsolin. Strikingly apparent is that the long helix in V6 is straight, as found in the activated form of G6, as opposed to the kinked version in inactive gelsolin. Molecular dynamics calculations suggest that the preferable conformation for this helix in the isolated G6 domain is also straight in the absence of Ca2+ and other gelsolin domains. However, the G6 helix bends in intact calcium ion-free gelsolin to allow interaction with G2 and G4. We suggest that a similar situation exists in villin. Within the intact protein, a bent V6 helix, when triggered by Ca2+, straightens and helps push apart adjacent domains to expose actin-binding sites within the protein. The sixth domain in this superfamily of proteins serves as a keystone that locks together a compact ensemble of domains in an inactive state. Perturbing the keystone initiates reorganization of the structure to reveal previously buried actin-binding sites.},
	keywords = {BINDING PROTEINS, calcium, COMPLEX, DOMAINS, F-ACTIN, HEADPIECE, SITES, SWITCH, TERMINAL HALF, VILLIN},
	isbn = {0021-9258},
	url = {<Go to ISI>://000268564400020},
	author = {Wang, H. and Chumnarnsilpa, S. and Loonchanta, A. and Li, Q. and Kuan, Y. M. and Robine, S. and Larsson, M. and Mihalek, I. and Burtnick, L. D. and Robinson, R. C.}
}
@article {2456,
	title = {Nanomechanical Properties of Tenascin-X Revealed by Single-Molecule Force Spectroscopy},
	journal = {Journal of Molecular Biology},
	volume = {385},
	number = {4},
	year = {2009},
	note = {ISI Document Delivery No.: 403HJTimes Cited: 4Cited Reference Count: 35Jollymore, Ashlee Lethias, Claire Peng, Qing Cao, Yi Li, Hongbin},
	month = {Jan},
	pages = {1277-1286},
	type = {Article},
	abstract = {Tenascin-X is an extracellular matrix protein and binds a variety of molecules in extracellular matrix and on cell membrane. Tenascin-X plays important roles in regulating the structure and mechanical properties of connective tissues. Using single-molecule atomic force microscopy, we have investigated the mechanical properties of bovine tenascin-X in detail. Our results indicated that tenascin-X is an elastic protein and the fibronectin type III (FnIII) domains can unfold under a stretching force and refold to regain their mechanical stability upon the removal of the stretching force. All the 30 FnIII domains of tenascin-X show similar mechanical stability, mechanical unfolding kinetics, and contour length increment upon domain unfolding, despite their large sequence diversity. In contrast to the homogeneity in their mechanical unfolding behaviors, FnIII domains fold at different rates. Using the 10th FnIII domain of tenascin-X (TNXfn10) as a model system, we constructed a polyprotein chimera composed of alternating TNXfn10 and GB1 domains and used. atomic force microscopy to confirm that the mechanical properties of TNXfn10 are consistent with those of the FnIII domains of tenascin-X These results lay the foundation to further study the mechanical properties of individual FnIII domains and establish the relationship between point mutations and mechanical phenotypic effect on tenascin-X Moreover, our results provided the opportunity to compare the mechanical properties and design of different forms of tenascins. The comparison between tenascin-X and tenascin-C revealed interesting common as well as distinguishing features for mechanical unfolding and folding of tenascin-C and tenascin-X and will open up new avenues to investigate the mechanical. functions and architectural design of different forms of tenascins. (C) 2008 Elsevier Ltd. All rights reserved.},
	keywords = {AFM, BINDING, DEFICIENCY, DOMAINS, FAMILY, FnIII domains, IDENTIFICATION, III MODULES, MECHANICAL STABILITY, mechanical unfolding, microscopy, PROTEIN, single molecule force spectroscopy, tenascin},
	isbn = {0022-2836},
	url = {<Go to ISI>://000263073400022},
	author = {Jollymore, A. and Lethias, C. and Peng, Q. and Cao, Y. and Li, H. B.}
}
@article {2033,
	title = {Engineered elastomeric proteins with dual elasticity can be controlled by a molecular regulator},
	journal = {Nature Nanotechnology},
	volume = {3},
	number = {8},
	year = {2008},
	note = {ISI Document Delivery No.: 335WZTimes Cited: 12Cited Reference Count: 29Cao, Yi Li, Hongbin},
	month = {Aug},
	pages = {512-516},
	type = {Article},
	abstract = {Elastomeric proteins are molecular springs that confer excellent mechanical properties(1-5) to many biological tissues and biomaterials. Depending on the role performed by the tissue or biomaterial, elastomeric proteins can behave as molecular springs(1,2,6,7) or shock absorbers(3-5,8-10). Here we combine single-molecule atomic force microscopy and protein engineering techniques to create elastomeric proteins that can switch between two distinct types of mechanical behaviour in response to the binding of a molecular regulator. The proteins are mechanically labile by design and behave as entropic springs with an elasticity that is governed by their configurational entropy. However, when a molecular regulator binds to the protein, it switches into a mechanically stable state and can act as a shock absorber. These engineered proteins effectively mimic and combine the two extreme forms of elastic behaviour found in natural elastomeric proteins, and thus represent a new type of smart nanomaterial that will find potential applications in nanomechanics and material sciences.},
	keywords = {BINDING, BIOLOGICAL ROLES, DESIGN, DOMAINS, FORCE-SPECTROSCOPY, MECHANICAL-PROPERTIES, STABILITY, TITINS, TOPOLOGY},
	isbn = {1748-3387},
	url = {<Go to ISI>://000258325800018},
	author = {Cao, Y. and Li, H. B.}
}
@article {2034,
	title = {Single molecule force spectroscopy reveals engineered metal chelation is a general approach to enhance mechanical stability of proteins},
	journal = {Proceedings of the National Academy of Sciences of the United States of America},
	volume = {105},
	number = {32},
	year = {2008},
	note = {ISI Document Delivery No.: 339EKTimes Cited: 16Cited Reference Count: 44Cao, Yi Yoo, Teri Li, Hongbin},
	month = {Aug},
	pages = {11152-11157},
	type = {Article},
	abstract = {Significant mechanical stability is an essential feature shared by many elastomeric proteins, which function as molecular springs in a wide variety of biological machinery and biomaterials of superb mechanical properties. Despite the progress in understanding molecular determinants of mechanical stability, it remains challenging to rationally enhance the mechanical stability of proteins. Using single molecule force spectroscopy and protein engineering techniques, we demonstrate that engineered bi-histidine metal chelation can enhance the mechanical stability of proteins significantly and reversibly. Based on simple thermodynamic cycle analysis, we engineered a bi-histidine metal chelation site into various locations of the small protein, GB1, to achieve preferential stabilization of the native state over the mechanical unfolding transition state of GB1 through the binding of metal ions. Our results demonstrate that the metal chelation can enhance the mechanical stability of GB1 by as much as 100 pN. Since bi-histidine metal chelation sites can be easily implemented, engineered metal chelation provides a general methodology to enhance the mechanical stability of a wide variety of proteins. This general approach in protein mechanics will enable the rational tuning of the mechanical stability of proteins. It will not only open new avenues toward engineering proteins of tailored nanomechanical properties, but also provide new approaches to systematically map the mechanical unfolding pathway of proteins.},
	keywords = {BINDING SITES, charge, DESIGN, DOMAINS, ELASTICITY, engineering, EXTRACELLULAR-MATRIX PROTEIN, mechanical unfolding, PROTEIN, protein mechanics, rational design, SIMULATIONS, STABILIZATION, STRENGTH, THERMOSTABILITY, TITIN},
	isbn = {0027-8424},
	url = {<Go to ISI>://000258560700024},
	author = {Cao, Y. and Yoo, T. and Li, H. B.}
}
@article {1368,
	title = {Calcium ion exchange in crystalline gelsolin},
	journal = {Journal of Molecular Biology},
	volume = {357},
	number = {3},
	year = {2006},
	note = {ISI Document Delivery No.: 030IYTimes Cited: 6Cited Reference Count: 24},
	month = {Mar},
	pages = {773-782},
	type = {Article},
	abstract = {Gelsolin is a calcium and pH-sensitive modulator of actin filament length. Here, we use X-ray crystallography to examine the extraction and exchange of calcium ions from their binding sites in different crystalline forms of the activated N and C-terminal halves of gelsolin, G1-G3 and G4-G6, respectively. We demonstrate that the combination of calcium and low pH activating conditions do not induce conformational changes in G4-G6 beyond those elicited by calcium alone. EGTA is able to remove calcium ions bound to the type I and type II metal ion-binding sites in G4-G6. Constrained by crystal contacts and stabilized by interdomain interaction surfaces, the gross structure of calcium-depleted G4-G6 remains that of the activated form. However, high-resolution details of changes in the ion-binding sites may represent the initial steps toward restoration of the arrangement of domains found in the calcium-free inactive form of gelsolin in solution. Furthermore, bathing crystals with the trivalent calcium ion mimic, Tb3+, results in anomalous scattering data that permit unequivocal localization of terbium ions in each of the proposed type I and type II ion-binding sites of both halves of gelsolin. In contrast to predictions based on solution studies, we find that no calcium ion is immune to exchange. (c) 2006 Elsevier Ltd. All rights reserved.},
	keywords = {actin, ACTIN MONOMER, ACTIVATION, apoptosis, BINDING-SITE, C-TERMINAL HALF, calcium activation, COMPLEX, CONFORMATIONAL CHANGE, DOMAINS, ELECTRON-DENSITY MAPS, gelsolin, IDENTIFICATION, MECHANISMS, protein crystallography},
	isbn = {0022-2836},
	url = {<Go to ISI>://000236629300008},
	author = {Chumnarnsilpa, S. and Loonchanta, A. and Xue, B. and Choe, H. and Urosev, D. and Wang, H. and Lindberg, U. and Burtnick, L. D. and Robinson, R. C.}
}
@article {697,
	title = {Activation in isolation: exposure of the actin-binding site in the C-terminal half of gelsolin does not require actin},
	journal = {Febs Letters},
	volume = {552},
	number = {2-3},
	year = {2003},
	note = {ISI Document Delivery No.: 726DKTimes Cited: 15Cited Reference Count: 23},
	month = {Sep},
	pages = {82-85},
	type = {Article},
	abstract = {Gelsolin requires activation to carry out its severing and capping activities on F-actin. Here, we present the structure of the isolated C-terminal half of gelsolin (G4-G6) at 2.0 resolution in the presence of Ca2+ ions. This structure completes a triptych of the states of activation of G4-G6 that illuminates its role in the function of gelsolin. Activated G4-G6 displays an open conformation, with the actin-binding site on G4 fully exposed and all three type-2 Ca2+ sites occupied. Neither actin nor the type-1 Ca2+, which normally is sandwiched between actin and G4, is required to achieve this conformation. (C) 2003 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.},
	keywords = {actin, calcium-activation, COMPLEX, DOMAINS, F-ACTIN, gelsolin, PLASMA GELSOLIN, REGULATORY PROTEIN, TRANSFORMATION},
	isbn = {0014-5793},
	url = {<Go to ISI>://000185583000002},
	author = {Narayan, K. and Chumnarnsilpa, S. and Choe, H. and Irobi, E. and Urosev, D. and Lindberg, U. and Schutt, C. E. and Burtnick, L. D. and Robinson, R. C.}
}
