Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Serum gelsolin, a Ca2+-dependent protein regulating the length of actin filaments, undergoes conformational changes upon binding Ca2+. These were detected and analyzed by several approaches including ultraviolet difference spectroscopy, circular dichroism studies, analytical ultracentrifugation, thiol group titration, and limited proteolytic digestions. The effect of Ca2+ binding on the UV absorption difference spectrum and the near-UV circular dichroism spectrum was consistent with changes in the environments of tyrosine and phenylalanine residues. In the presence of Ca2+, the S0(20),w value decreased from 5.3 to 4.7. This latter result implies a transformation to a more asymmetric molecular shape. Gelsolin contained only two accessible thiol groups per mole of protein, one of which was titratable in the native protein; it was more accessible to 5,5'-dithiobis(2-nitrobenzoic acid) in the absence than in the presence of Ca2+. The limited digestion of gelsolin from serum and bovine aorta smooth muscle by two different proteases, chymotrypsin and trypsin, proceeded much faster in the presence of Ca2+ than in its absence with the production of three main fragments of about 40K, 32K, and 21K. This fragment mixture was found still able to shorten F-actin in a Ca2+-dependent manner; this severing activity was expressed by the isolated 40K peptide. Gelsolin was cross-linked to F- and G-actin by the zero-length cross-linker 1-ethyl-3-[3-(dimethylamino)propyl]-carbodiimide (EDC), generating a covalent 130K binary complex (actin1-gelsolin1) followed by a covalent 180K ternary complex (actin2-gelsolin1).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characterization of the Ca2+-induced conformational changes in gelsolin and identification of interaction regions between actin and gelsolin. 301 7

Under nondenaturing conditions, 1 mol of horse plasma gelsolin reacts with 1.9 +/- 0.5 mol (mean +/- SD, n = 6) of the sulfhydryl-specific fluorescent reagent 6-acryloyl-2-dimethylaminonaphthalene (acrylodan). The degree of labeling in 6 M guanidine-HCl increases to about 3 mol of acrylodan per mole of gelsolin. Viscosity studies show that the modified gelsolin retains its ability to sever F-actin filaments. Circular dichroism spectra in the peptide bond absorption region are indistinguishable for labeled and unmodified gelsolin at room temperature. The thermal stability of gelsolin, as monitored by circular dichroism, is unaffected by reaction with acrylodan. While circular dichroism spectra of acrylodan-labeled gelsolin recorded at room temperature are not influenced significantly by Ca2+, fluorescence studies reveal a number of Ca(2+)-dependent changes in the protein. Ca2+ causes a decrease and red-shift in fluorescence emission, an increase in sensitivity to quenching by I-, and a decrease in polarization of the fluorescence of acrylodan-labeled gelsolin. Together, these changes in fluorescence properties indicate there to be an increased exposure of the label to the solvent when gelsolin binds Ca2+. Fluorescence polarization experiments in which acrylodan-labeled gelsolin is titrated with actin emphasize that Ca2+ is required for these two proteins to interact.
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PMID:Fluorescent responses of acrylodan-labeled plasma gelsolin. 838 3

Fluorescent derivatives of phosphatidyl inositol (PtdIns)-(4,5)-P2 were synthesized and used to test the effects of the PtdIns-(4, 5)-P2-regulated proteins gelsolin, tau, cofilin, and profilin on labeled PtdIns-(4,5)-P2 that was either in micellar form or mixed with phosphatidylcholine (PtdCho) in bilayer vesicles. Gelsolin increased the fluorescence of 7-nitrobenz-2-oxa-1,3-diazole (NBD)- or pyrene-labeled PtdIns-(4,5)-P2 and NBD-PtdIns-(3,4,5)-P3. Cofilin and profilin produced no detectable change at equimolar ratios to PtdIns-(4,5)-P2, while tau decreased NBD-PtdIns-(4,5)-P2 fluorescence. Fluorescence enhancement by gelsolin of NBD-PtdIns-(4, 5)-P2 in mixed lipid vesicles depended on the mole fraction of PtdIns-(4,5)-P2 in the bilayer. Specific enhancement of 3% NBD-PtdIns-(4,5)-P2 : 97% PtdCho was much lower than that of 10% PtdIns-(4,5)-P2 : 90% PtdCho, but the enhancement of 3% NBD-PtdIns-(4,5)-P2 could be increased by addition of 7% unlabeled PtdIns-(4,5)-P2. The gelsolin-dependent increase in NBD-PtdIns-(4, 5)-P2 fluorescence was reversed by addition of Ca2+ or G-actin. Significant, but weaker, fluorescence enhancement was observed with the gelsolin N-terminal domain (residues 1-160) and a peptide comprised of gelsolin residues 150-169. Fluorescence energy transfer from gelsolin to pyrene-PtdIns-(4,5)-P2 was much stronger with intact gelsolin than the N-terminal region of gelsolin containing the PtdIns-(4,5)-P2 binding sites, suggesting that PtdIns-(4,5)-P2 may bind near a site formed by the juxtaposition of the N- and C-terminal domains of gelsolin.
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PMID:Fluorescent phosphoinositide derivatives reveal specific binding of gelsolin and other actin regulatory proteins to mixed lipid bilayers. 1042 91

The lateral distribution of phosphatidylinositol 4,5-bisphosphate (PIP2) in lipid bilayers is affected both by divalent cation-mediated attractions and cholesterol-dependent phase demixing. The effects of lateral redistribution of PIP2 within a membrane on PIP2-protein interactions are explored with an N-terminal fragment of gelsolin (NtGSN) that severs actin in a Ca(2+)-insensitive manner. The extent of NtGSN inhibition by PIP2-containing large unilamellar vesicles (LUVs) depends on the lateral organization of the membrane as quantified by an actin-severing assay. At a fixed PIP2 mole fraction, the inhibition is largely enhanced by the segregation of liquid ordered/liquid disordered (Lo/Ld) phases that is induced by altering either cholesterol content or temperature, whereas the presence of Ca(2+) only slightly improves the inhibition. Inhibition of gelsolin induced by demixed LUVs is more effective with decreasing temperature, coincident with increasing membrane order as determined by Laurdan generalized polarization and is reversible as the temperature increases. This result suggests that PIP2-mediated inhibition of gelsolin function depends not only on changes in global concentration but also on lateral distribution of PIP2. These observations imply that gelsolin, and perhaps other PIP2-regulated proteins, can be activated or inactivated by the formation of nanodomains or clusters without changing PIP2 bulk concentration in the cell membrane.
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PMID:Cholesterol-Dependent Phase-Demixing in Lipid Bilayers as a Switch for the Activity of the Phosphoinositide-Binding Cytoskeletal Protein Gelsolin. 2722 9