scholarly journals Evidence for similar conformational changes in α2-macroglobulin on reaction with primary amines or proteolytic enzymes

1982 ◽  
Vol 207 (2) ◽  
pp. 347-356 ◽  
Author(s):  
Ingemar Björk ◽  
Wayne W. Fish
Keyword(s):  
Circular Dichroism ◽  
Conformational Change ◽  
Conformational Changes ◽  
Enzyme Inhibitor ◽  
Proteolytic Enzymes ◽  
Sedimentation Coefficient ◽  
Primary Amines ◽  
Hydrodynamic Volume ◽  
Α2 Macroglobulin ◽  
Circular Dichroïsm

Reactions of α2-macroglobulin (α2M) with primary amines (ammonium chloride, methylammonium chloride and ethylammonium chloride) or proteolytic enzymes (trypsin, chymotrypsin and thrombin) resulted in changes of the absorption, fluorescence and circular-dichroism spectra and of the sedimentation coefficient of the inhibitor. All physico-chemical changes caused by the inactivation of α2M by the amines were identical with, or highly similar to, those induced by the formation of the enzyme–inhibitor complexes. This suggests that similar conformational changes of the inhibitor occur in the two types of reactions. The frictional ratio, calculated from the increase in sedimentation coefficient, decreased from 1.67 for untreated α2M to 1.57 for the amine- or proteinase-treated inhibitor. This change is due to a decrease in either asymmetry or hydration of the protein, resulting in a slightly smaller hydrodynamic volume. The circular-dichroism analyses indicated that the reaction of α2M with either amines or proteinases is accompanied by a loss of the small amount (about 5%) of α-helix of the untreated protein. The changes of u.v. absorption and fluorescence suggested that about one out of the eight to ten tryptophan residues of each α2M subunit is buried as a result of the conformational change. All spectroscopic and hydrodynamic changes that were observed are compatible with a spatial rearrangement of the subunits of α2M, as implicated by the ‘trap’ hypothesis for the mechanism of inhibition of proteinases. However, a conformational change involving a decrease in the hydrodynamic volume of each subunit cannot be excluded.

scholarly journals Conformational changes in the H3 . H4 histone complex. Serological and circular dichroism studies.

1980 ◽  
Vol 255 (15) ◽  
pp. 7059-7062
Author(s):  
L. Feldman ◽  
N.V. Beaudette ◽  
B.D. Stollar ◽  
G.D. Fasman
Keyword(s):  
Circular Dichroism ◽  
Conformational Changes ◽  
Circular Dichroïsm

scholarly journals Electronic Circular Dichroism of the Cas9 Protein and gRNA:Cas9 Ribonucleoprotein Complex

2021 ◽  
Vol 22 (6) ◽  
pp. 2937
Author(s):  
Monika Halat ◽  
Magdalena Klimek-Chodacka ◽  
Jagoda Orleanska ◽  
Malgorzata Baranska ◽  
Rafal Baranski
Keyword(s):  
Circular Dichroism ◽  
Conformational Changes ◽  
Structural Changes ◽  
Electronic Circular Dichroism ◽  
Guide Rna ◽  
Cas9 Protein ◽  
Rnp Complex ◽  
Characteristic Features ◽  
Circular Dichroïsm

The Streptococcus pyogenes Cas9 protein (SpCas9), a component of CRISPR-based immune system in microbes, has become commonly utilized for genome editing. This nuclease forms a ribonucleoprotein (RNP) complex with guide RNA (gRNA) which induces Cas9 structural changes and triggers its cleavage activity. Here, electronic circular dichroism (ECD) spectroscopy was used to confirm the RNP formation and to determine its individual components. The ECD spectra had characteristic features differentiating Cas9 and gRNA, the former showed a negative/positive profile with maxima located at 221, 209 and 196 nm, while the latter revealed positive/negative/positive/negative pattern with bands observed at 266, 242, 222 and 209 nm, respectively. For the first time, the experimental ECD spectrum of the gRNA:Cas9 RNP complex is presented. It exhibits a bisignate positive/negative ECD couplet with maxima at 273 and 235 nm, and it differs significantly from individual spectrum of each RNP components. Additionally, the Cas9 protein and RNP complex retained biological activity after ECD measurements and they were able to bind and cleave DNA in vitro. Hence, we conclude that ECD spectroscopy can be considered as a quick and non-destructive method of monitoring conformational changes of the Cas9 protein as a result of Cas9 and gRNA interaction, and identification of the gRNA:Cas9 RNP complex.

scholarly journals The effects of Ca2+ and Cd2+ on the secondary and tertiary structure of bovine testis calmodulin. A circular-dichroism study

1986 ◽  
Vol 238 (2) ◽  
pp. 485-490 ◽  
Author(s):  
S R Martin ◽  
P M Bayley
Keyword(s):  
Circular Dichroism ◽  
Conformational Changes ◽  
Metal Ion ◽  
Tertiary Structure ◽  
Thermal Unfolding ◽  
Apparent Effect ◽  
Thermally Induced ◽  
Circular Dichroïsm ◽  
Secondary And Tertiary Structure

Near-u.v. and far-u.v. c.d. spectra of bovine testis calmodulin and its tryptic fragments (TR1C, N-terminal half, residues 1-77, and TR2C, C-terminal half, residues 78-148) were recorded in metal-ion-free buffer and in the presence of saturating concentrations of Ca2+ or Cd2+ under a range of different solvent conditions. The results show the following: if there is any interaction between the N-terminal and C-terminal halves of calmodulin, it has not apparent effect on the secondary or tertiary structure of either half; the conformational changes induced by Ca2+ or Cd2+ are substantially greater in TR2C than they are in TR1C; the presence of Ca2+ or Cd2+ confers considerable stability with respect to urea-induced denaturation, both for the whole molecule and for either of the tryptic fragments; a thermally induced transition occurs in whole calmodulin at temperatures substantially below the temperature of major thermal unfolding, both in the presence and in the absence of added metal ion; the effects of Cd2+ are identical with those of Ca2+ under all conditions studied.

Germin: physicochemical properties of the glycoprotein which signals onset of growth in the germinating wheat embryo

1987 ◽  
Vol 65 (12) ◽  
pp. 1039-1048 ◽  
Author(s):  
William C. McCubbin ◽  
Cyril M. Kay ◽  
Theresa D. Kennedy ◽  
Byron G. Lane
Keyword(s):  
Circular Dichroism ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Sedimentation Coefficient ◽  
Helical Structure ◽  
Random Coil ◽  
Sedimentation Equilibrium ◽  
Cross Linking ◽  
Wheat Embryo ◽  
Circular Dichroïsm

The size and structure of germin, the homooligomeric glycoprotein which marks the onset of growth in germinating wheat embryos, has been examined by gel filtration, ultracentrifugation, electron microscopy, chemical cross-linking, and optical techniques (circular dichroism). Germin has a sedimentation coefficient (S20,w) of 7.3S, and a Stokes' radius (RS) of 4.5 nm, the latter value being compatible with the dimensions of the particle observed by negative staining in the electron microscope. By three methods (sedimentation equilibrium, sodium dodecyl sulphate (SDS) – polyacrylamide electrophoresis, S20,w/RS), the mean particle mass of the two closely related forms of germin (G and G′) is ca. 130 kilodaltons (kDa). Cross-linking with dimethyl suberimidate indicates that the oligomer is homopentameric, compatible with the molecular mass of the protomer (ca. 26 kDa) as determined by SDS–polyacrylamide gel electrophoresis. Using the Provencher and Glockner analysis to interpret circular dichroism measurements (in the far ultraviolet), both forms of germin contain about 10–20% α-helical structure, 50–60% β-sheet/turn structure, and 20–30% random coil. In a structure-inducing environment (45% trifluoroethanol), the α-helical structure increases to a value (35–40%) similar to that predicted by Chou–Fasman analysis of the protein sequence deduced by cDNA sequencing.

Circular dichroism studies of freeze-drying-induced conformational changes in human hemoglobin

Biopolymers ◽  
1983 ◽  
Vol 22 (11) ◽  
pp. 2367-2381 ◽  
Author(s):  
Christian Thirion ◽  
Dominique Larcher ◽  
Bernard Chaillot ◽  
Pierre Labrude ◽  
Claude Vigneron
Keyword(s):  
Circular Dichroism ◽  
Conformational Changes ◽  
Freeze Drying ◽  
Human Hemoglobin ◽  
Circular Dichroïsm
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