@article {2546,
	title = {Ca2+ binding by domain 2 plays a critical role in the activation and stabilization of gelsolin},
	journal = {Proceedings of the National Academy of Sciences of the United States of America},
	volume = {106},
	number = {33},
	year = {2009},
	note = {ISI Document Delivery No.: 484WETimes Cited: 5Cited Reference Count: 30Nag, Shalini Ma, Qing Wang, Hui Chumnarnsilpa, Sakesit Lee, Wei Lin Larsson, Marten Kannan, Balakrishnan Hernandez-Valladarez, Maria Burtnick, Leslie D. Robinson, Robert C.},
	month = {Aug},
	pages = {13713-13718},
	type = {Article},
	abstract = {Gelsolin consists of six homologous domains (G1-G6), each containing a conserved Ca-binding site. Occupation of a subset of these sites enables gelsolin to sever and cap actin filaments in a Ca-dependent manner. Here, we present the structures of Ca-free human gelsolin and of Ca-bound human G1-G3 in a complex with actin. These structures closely resemble those determined previously for equine gelsolin. However, the G2 Ca-binding site is occupied in the human G1-G3/actin structure, whereas it is vacant in the equine version. In-depth comparison of the Ca-free and Ca-activated, actin-bound human gelsolin structures suggests G2 and G6 to be cooperative in binding Ca2+ and responsible for opening the G2-G6 latch to expose the F-actin-binding site on G2. Mutational analysis of the G2 and G6 Ca-binding sites demonstrates their interdependence in maintaining the compact structure in the absence of calcium. Examination of Ca binding by G2 in human G1-G3/actin reveals that the Ca2+ locks the G2-G3 interface. Thermal denaturation studies of G2-G3 indicate that Ca binding stabilizes this fragment, driving it into the active conformation. The G2 Ca-binding site is mutated in gelsolin from familial amyloidosis (Finnish-type) patients. This disease initially proceeds through protease cleavage of G2, ultimately to produce a fragment that forms amyloid fibrils. The data presented here support a mechanism whereby the loss of Ca binding by G2 prolongs the lifetime of partially activated, intermediate conformations in which the protease cleavage site is exposed.},
	keywords = {actin, AMYLOIDOGENESIS, biosynthesis, calcium, calcium activated, calcium dependent, FAMILIAL AMYLOIDOSIS, IDENTIFICATION, PLASMA GELSOLIN, PROTEIN, SITE, TERMINAL HALF, TIRF},
	isbn = {0027-8424},
	url = {<Go to ISI>://000269078700018},
	author = {Nag, S. and Ma, Q. and Wang, H. and Chumnarnsilpa, S. and Lee, W. L. and Larsson, M. and Kannan, B. and Hernandez-Valladarez, M. and Burtnick, L. D. and Robinson, R. C.}
}
@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 {1612,
	title = {The structure of gelsolin bound to ATP},
	journal = {Journal of Molecular Biology},
	volume = {357},
	number = {3},
	year = {2006},
	note = {ISI Document Delivery No.: 030IYTimes Cited: 7Cited Reference Count: 28},
	month = {Mar},
	pages = {765-772},
	type = {Article},
	abstract = {Calcium activation of the actin-modifying properties of gelsolin is sensitive to ATP. Here, we show that soaking calcium-free gelsolin crystals in ATP-containing media results in ATP occupying a site that spans the two pseudosymmetrical halves of the protein. ATP binding involves numerous polar and hydrophobic contacts and is identical for the two copies of gelsolin related by non-crystallographic symmetry within the crystal. The gamma-phosphate of ATP participates in several charge-charge interactions consistent with the preference of gelsolin for ATP, as a binding partner, over ADP. In addition, disruption of the ATP-binding site through Ca2+ activation of gelsolin reveals why ATP binds more tightly to the inactive molecule, and suggests how the binding of ATP may modulate the sensitivity of gelsolin to calcium ions. Similarities between the ATP and PIP2 interactions with the C-terminal half of gelsolin are evident from their overlapping binding sites and in that both molecules bind more tightly in the absence of calcium ions. We propose a model for how PIP2 may bind to calcium-free gelsolin based on the ATP-binding site. (c) 2006 Elsevier Ltd. All rights reserved.},
	keywords = {5-BISPHOSPHATE, actin, ATP, BINDING-SITE, calcium, CRYSTAL-STRUCTURE, DOMAIN, gelsolin, HUMAN-PLASMA GELSOLIN, IDENTIFICATION, PHOSPHATIDYLINOSITOL 4, PIP2, PROTEIN, TERMINAL HALF},
	isbn = {0022-2836},
	url = {<Go to ISI>://000236629300007},
	author = {Urosev, D. and Ma, Q. and Tan, A. L. C. and Robinson, R. C. and Burtnick, L. D.}
}
@article {813,
	title = {Structure of the N-terminal half of gelsolin bound to actin: roles in severing, apoptosis and FAF},
	journal = {Embo Journal},
	volume = {23},
	number = {14},
	year = {2004},
	note = {ISI Document Delivery No.: 847NBTimes Cited: 41Cited Reference Count: 59},
	month = {Jul},
	pages = {2713-2722},
	type = {Article},
	abstract = {The actin filament-severing functionality of gelsolin resides in its N-terminal three domains (G1 - G3). We have determined the structure of this fragment in complex with an actin monomer. The structure reveals the dramatic domain rearrangements that activate G1 - G3, which include the replacement of interdomain interactions observed in the inactive, calcium-free protein by new contacts to actin, and by a novel G2 - G3 interface. Together, these conformational changes are critical for actin filament severing, and we suggest that their absence leads to the disease Finnish-type familial amyloidosis. Furthermore, we propose that association with actin drives the calcium-independent activation of isolated G1 G3 during apoptosis, and that a similar mechanism operates to activate native gelsolin at micromolar levels of calcium. This is the first structure of a filament-binding protein bound to actin and it sets stringent, high-resolution limitations on the arrangement of actin protomers within the filament.},
	keywords = {5-BISPHOSPHATE, actin, AMYLOIDOSIS-FINNISH TYPE, apoptosis, BINDING-SITE, CA2+ REGULATION, calcium, CRYSTAL-STRUCTURE, crystallographic structure, F-ACTIN, FAMILIAL AMYLOIDOSIS, FILAMENT BARBED ENDS, gelsolin, PHOSPHATIDYLINOSITOL 4, PLASMA GELSOLIN, X-RAY},
	isbn = {0261-4189},
	url = {<Go to ISI>://000223398800002},
	author = {Burtnick, L. D. and Urosev, D. and Irobi, E. and Narayan, K. and Robinson, R. C.}
}
@article {643,
	title = {From the first to the second domain of gelsolin: a common path on the surface of actin?},
	journal = {Febs Letters},
	volume = {552},
	number = {2-3},
	year = {2003},
	note = {ISI Document Delivery No.: 726DKTimes Cited: 22Cited Reference Count: 29},
	month = {Sep},
	pages = {86-90},
	type = {Article},
	abstract = {We present the 2.6. resolution crystal structure of a complex formed between G-actin and gelsolin fragment Met25-GIn160 (G1+). The structure differs from those of other gelsolin domain 1 (G1) complexes in that an additional six amino acid residues from the crucial linker region into gelsolin domain 2 (G2) are visible and are attached securely to the surface of actin. The linker segment extends away from G1 up the face of actin in a direction that infers G2 will bind along the same long-pitch helical strand as the actin bound to G1. This is consistent with a mechanism whereby G2 attaches gelsolin to the side of a filament and then directs G1 toward a position where it would disrupt actin-actin contacts. Alignment of the sequence of the structurally important residues within the G1-G2 linker with those of WH2 (WASp homology domain 2) domain protein family members (e.g. WASp (Wiscott-Aldridge syndrome protein) and thymosin beta4) suggests that the opposing activities of filament assembly and disassembly may exploit a common patch on the surface of actin. (C) 2003 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.},
	keywords = {actin, BINDING, calcium, COMPLEX, crystal structure, DIFFRACTION DATA, F-ACTIN, FILAMENT, gelsolin, IDENTIFICATION, MODEL, MOTILITY, NUCLEATION, WH2 domain},
	isbn = {0014-5793},
	url = {<Go to ISI>://000185583000003},
	author = {Irobi, E. and Burtnick, L. D. and Urosev, D. and Narayan, K. and Robinson, R. C.}
}
@article {348,
	title = {The calcium activation of gelsolin: Insights from the 3 angstrom structure of the G4-G6/actin complex},
	journal = {Journal of Molecular Biology},
	volume = {324},
	number = {4},
	year = {2002},
	note = {ISI Document Delivery No.: 625PRTimes Cited: 48Cited Reference Count: 32},
	month = {Dec},
	pages = {691-702},
	type = {Article},
	abstract = {Gelsolin participates in the reorganization of the actin cytoskeleton that is required during such phenomena as cell movement, cytokinesis, and apoptosis. It consists of six structurally similar domains, G1-G6, which are arranged at resting intracellular levels of calcium ion so as to obscure the three actin-binding surfaces. Elevation of Ca2+ concentrations releases latches within the constrained structure and produces large shifts in the relative positioning of the domains, permitting gelsolin to bind to and sever actin filaments. How Ca2+ is able to activate gelsolin has been a major question concerning the function of this protein. We present the improved structure of the C-terminal half of gelsolin bound to monomeric actin at 3.0 Angstrom resolution. Two classes of Ca2+-binding site are evident on gelsolin: type 1 sites share coordination of Ca2+ with actin, while type 2 sites are wholly contained within gelsolin. This structure of the complex reveals the locations of two novel metal ion-binding sites in domains G5 and G6, respectively. We identify both as type 2 sites. The absolute conservation of the type 2 calcium-ligating residues across the six,domains of gelsolin suggests that this site exists in each of the domains. In total, gelsolin has the potential to bind eight calcium ions, two type 1 and six type 2. The function of the type 2 sites is to facilitate structural rearrangements within gelsolin as part of the activation and actin-binding and severing processes. We propose the novel type 2 site in G6 to be the critical site that initiates overall activation of gelsolin by releasing the tail latch that locks calcium-free gelsolin in a conformation unable to bind actin. (C) 2002 Elsevier Science Ltd. All rights reserved.},
	keywords = {actin, ACTIVATION, ACTOPHORIN, BINDING DOMAIN, CA2+, calcium, CAPPING PROTEIN, F-ACTIN, FAMILIAL AMYLOIDOSIS, FINNISH TYPE, gelsolin, IDENTIFICATION, MECHANISM, PLASMA GELSOLIN, REGULATION, severing},
	isbn = {0022-2836},
	url = {<Go to ISI>://000179825300011},
	author = {Choe, H. and Burtnick, L. D. and Mejillano, M. and Yin, H. L. and Robinson, R. C. and Choe, S.}
}
@article {4689,
	title = {Undercarboxylation of recombinant prothrombin revealed by analysis of gamma-carboxyglutamic acid using capillary electrophoresis and laser-induced fluorescence},
	journal = {Febs Letters},
	volume = {445},
	number = {2-3},
	year = {1999},
	note = {ISI Document Delivery No.: 175YCTimes Cited: 6Cited Reference Count: 37},
	month = {Feb},
	pages = {256-260},
	type = {Article},
	abstract = {The gamma-carboxyglutamic acid (Gla) content of several variants of human prothrombin has been measured by using capillary electrophoresis and laser-induced fluorescence (CE-LIF). Both plasma-derived prothrombin and recombinant prothrombin contain ten residues of Gla per molecule of protein. In contrast, a variant of human prothrombin (containing the second kringle domain of bovine prothrombin) was separated into two populations that differed in their Gla content. Direct measurement of the Gla content showed an association with the presence or absence of the calcium-dependent conformational change that is required for prothombinase function. Thus, the CE-LIF assay is useful in determining the carboxylation status of recombinant proteins. (C) 1999 Federation of European Biochemical Societies.},
	keywords = {baby hamster kidney, calcium, capillary electrophoresis, cell, EXPRESSION, FACTOR-X, gamma carboxy glutamic acid, GLUTAMIC-ACID, HUMAN PROTEIN-C, LASER-INDUCED FLUORESCENCE, METAL, PHOSPHOLIPID-BINDING-PROPERTIES, PROTHROMBIN, PURIFICATION, recombinant protein, RESIDUES, VITAMIN-K},
	isbn = {0014-5793},
	url = {<Go to ISI>://000079122800007},
	author = {Vo, H. C. and Britz-McKibbin, P. and Chen, D. D. Y. and MacGillivray, R. T. A.}
}
@article {3920,
	title = {The crystal structure of plasma gelsolin: Implications for actin severing, capping, and nucleation},
	journal = {Cell},
	volume = {90},
	number = {4},
	year = {1997},
	note = {ISI Document Delivery No.: XT066Times Cited: 164Cited Reference Count: 50},
	month = {Aug},
	pages = {661-670},
	type = {Article},
	abstract = {The structure of gelsolin has been determined by crystallography and comprises six structurally related domains that, in a Ca2+-free environment, pack together to form a compact globular structure in which the putative actin-binding sequences are not sufficiently exposed to enable binding to occur. We propose that binding Ca2+ can release the connections that join the N- and C-terminal halves of gelsolin, enabling each half to bind actin relatively independently. Domain shifts are proposed in response to Ca2+ as bases for models of how gelsolin acts to sever, cap, or nucleate F-actin filaments. The structure also invites discussion of polyphosphoinositide binding to segment 2 and suggests how mutation at Asp-187 could initiate a series of events that lead to deposition of amyloid plaques, as observed in victims of familial amyloidosis (Finnish type).},
	keywords = {AMYLOIDOSIS, BINDING DOMAIN, calcium, DEFINITION, F-ACTIN, FILAMENT, IDENTIFICATION, PROTEIN, SEQUENCE, VILLIN},
	isbn = {0092-8674},
	url = {<Go to ISI>://A1997XT06600010},
	author = {Burtnick, L. D. and Koepf, E. K. and Grimes, J. and Jones, E. Y. and Stuart, D. I. and McLaughlin, P. J. and Robinson, R. C.}
}
@article {3720,
	title = {Multiple pathways for denaturation of horse plasma gelsolin},
	journal = {Biochemistry and Cell Biology-Biochimie Et Biologie Cellulaire},
	volume = {74},
	number = {1},
	year = {1996},
	note = {ISI Document Delivery No.: UE605Times Cited: 1Cited Reference Count: 38},
	pages = {101-107},
	type = {Article},
	abstract = {Gelsolin purified from horse plasma carries a surface charge distribution that greatly influences how the protein unfolds, aggregates, or precipitates as a function of temperature or concentration of chemical denaturant. Modification of gelsolin with fluorescein isothiocyanate replaces positive charges on amine groups with bulky, negatively charged fluorescein moieties. This postpones thermally induced precipitation by about 10 degrees C [Koepf, E.K., and Burtnick, L.D. 1993. Eur. J. Biochem. 212: 713-718]. Interaction with cations such as Ca2+ or guanidinium(+) also alters the surface charge on gelsolin. This affects the structure of the protein in solution, modifies the pathway for unfolding, and moderates the onset of precipitation induced by chemical denaturants or heat. Denaturation of gelsolin is not interpretable in terms of a simple two-state cooperative mechanism. The pathway to a denatured state and intermediate structures present along the way depend upon the agent used to unfold the protein.},
	keywords = {ACTIN-BINDING-SITES, calcium, chemical, circular dichroism, denaturation, FLUORESCEIN ISOTHIOCYANATE, gelsolin, PROTEIN, thermal},
	isbn = {0829-8211},
	url = {<Go to ISI>://A1996UE60500011},
	author = {Koepf, E. K. and Burtnick, L. D.}
}
