scholarly journals Autoinhibition of the formin Cappuccino in the absence of canonical autoinhibitory domains

2012 ◽  
Vol 23 (19) ◽  
pp. 3801-3813 ◽  
Author(s):  
Batbileg Bor ◽  
Christina L. Vizcarra ◽  
Martin L. Phillips ◽  
Margot E. Quinlan
Keyword(s):  
Circular Dichroism ◽  
Binding Site ◽  
Actin Polymerization ◽  
Intramolecular Interaction ◽  
Hydrodynamic Analysis ◽  
A Site ◽  
Circular Dichroïsm

Formins are a conserved family of proteins known to enhance actin polymerization. Most formins are regulated by an intramolecular interaction. The Drosophila formin, Cappuccino (Capu), was believed to be an exception. Capu does not contain conserved autoinhibitory domains and can be regulated by a second protein, Spire. We report here that Capu is, in fact, autoinhibited. The N-terminal half of Capu (Capu-NT) potently inhibits nucleation and binding to the barbed end of elongating filaments by the C-terminal half of Capu (Capu-CT). Hydrodynamic analysis indicates that Capu-NT is a dimer, similar to the N-termini of other formins. These data, combined with those from circular dichroism, suggest, however, that it is structurally distinct from previously described formin inhibitory domains. Finally, we find that Capu-NT binds to a site within Capu-CT that overlaps with the Spire-binding site, the Capu-tail. We propose models for the interaction between Spire and Capu in light of the fact that Capu can be regulated by autoinhibition.

Circular dichroism studies of the HIV-1 Rev protein and its specific RNA binding site

Biochemistry ◽  
1990 ◽  
Vol 29 (42) ◽  
pp. 9791-9795 ◽  
Author(s):  
Thomas J. Daly ◽  
James R. Rusche ◽  
Theodore E. Maione ◽  
Alan D. Frankel
Keyword(s):  
Circular Dichroism ◽  
Binding Site ◽  
Rna Binding ◽  
Circular Dichroïsm ◽  
Hiv 1 ◽  
Rev Protein

scholarly journals Interaction between phloretin and insulin: a spectroscopic study

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Sahri Yanti ◽  
Zhong-Wen Wu ◽  
Dinesh Chandra Agrawal ◽  
Wei-Jyun Chien
Keyword(s):  
Circular Dichroism ◽  
Spectroscopic Study ◽  
Binding Site ◽  
Fluorescence Analysis ◽  
The Body ◽  
Quenching Effect ◽  
Improve Insulin Resistance ◽  
Vis Spectroscopy ◽  
Α Helix ◽  
Circular Dichroïsm

AbstractDiabetes is among the top ten deadly diseases in the world. It occurs either when the pancreas does not produce enough insulin (INS) or when the body cannot effectively use the insulin it produces. Phloretin (PHL) has a biological effect that can treat diabetes. A spectroscopic study was carried out to explore the interaction between phloretin and insulin. UV/Vis spectroscopy, fluorescence spectroscopy, and circular dichroism spectropolarimeter were used in the study. UV/Vis spectra showed that the interaction between PHL and INS produced strong absorption at a wavelength of 282 nm. The fluorescence analysis results showed that the excitation and emission occurred at 280-nm and 305-nm wavelengths, respectively. Temperature changes did not affect INS emissions. However, the interaction of PHL–INS caused a redshift at 305 to 317 nm. Temperature affected the binding constant (Ka) and the binding site (n). Ka decreased with increasing temperature and increased the binding site. The thermodynamic parameters such as enthalpy (ΔH0) and entropy (ΔS0) each had a value of − 16,514 kJ/mol and 22.65 J/mol·K. PHL and INS interaction formed hydrogen bonds and hydrophobic interaction. The free energy (ΔG0) recorded was negative. PHL and INS interactions took place spontaneously. The quenching effect was dynamic and static. KD values were greater than KS. The higher the temperature, the less was KD and KS. The appearance of two negative signals on circular dichroism (CD) spectropolarimeter implies that phloretin could induce regional configuration changes in insulin. The addition of PHL has revealed that the proportion of α-helix in the insulin stabilizes its structure. Phloretin’s stabilization and enhancement of the α-helix structural configuration in insulin indicate that phloretin can improve insulin resistance.

Circular dichroism and fluorescence spectroscopic study on the interaction of bisdemethoxycurcumin and diacetylbisdemethoxycurcumin with human serum albumin

2010 ◽  
Vol 88 (2) ◽  
pp. 155-163 ◽  
Author(s):  
Fakhrossadat Mohammadi ◽  
Abdol-Khalegh Bordbar ◽  
Khosro Mohammadi ◽  
Adeleh Divsalar ◽  
Ali Akbar Saboury
Keyword(s):  
Circular Dichroism ◽  
Secondary Structure ◽  
Human Serum Albumin ◽  
Serum Albumin ◽  
Human Serum ◽  
Binding Site ◽  
Binding Parameters ◽  
Oh Groups ◽  
Fluorescence Measurements ◽  
Circular Dichroïsm

The interactions of bisdemethoxycurcumin (BDMC) as a bioactive constituent of turmeric and diacetylbisdemethoxycurcumin (DABC) as a novel synthetic derivative of curcumin with human serum albumin (HSA) have been investigated by fluorescence and circular dichroism (CD) spectroscopy. The binding parameters, including the number of substantive binding sites and the binding constants, have been estimated from the analysis of fluorescence measurements. The estimated binding parameters indicated that BDMC has higher affinity than DABC to bind HSA, suggesting the essential role of the phenolic OH groups of BDMC, which are acetylated in DABC. It was found that the binding site for BDMC and DABC is located in the vicinity of Trp-214 in subdomain IIA, which is the same as binding site for curcumin (CUR). The minor changes on the far-UV circular dichroism spectra resulted in partial changes in the calculated secondary structure contents of HSA. The negligible alteration in the secondary structure of HSA indicated that ligand-induced conformational changes are localized in the binding site and do not involve considerable changes in the protein folding. The visible CD spectra indicated that the optical activity observed during the ligand binding is due to induced-protein chirality.

scholarly journals The Cytokine IL-1β and Piperine Complex Surveyed by Experimental and Computational Molecular Biophysics

Biomolecules ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1337 ◽  
Author(s):  
Gabriel Zazeri ◽  
Ana Paula Ribeiro Povinelli ◽  
Marcelo de Freitas Lima ◽  
Marinônio Lopes Cornélio
Keyword(s):  
Circular Dichroism ◽  
Binding Site ◽  
Interleukin 1 ◽  
Umbrella Sampling ◽  
Affinity Constant ◽  
Interleukin 1 Beta ◽  
Biophysical Approach ◽  
Therapeutic Properties ◽  
First Time ◽  
Circular Dichroïsm

The bioactive piperine, a compound found in some pepper species, has been widely studied because of its therapeutic properties that include the inhibition of an important inflammation pathway triggered by interleukin-1 beta (IL-1β). However, investigation into the molecular interactions between IL-1β and piperine is not reported in the literature. Here, we present for the first time the characterisation of the complex formed by IL-1β and piperine through experimental and computational molecular biophysical analyses. Fluorescence spectroscopy unveiled the presence of one binding site for piperine with an affinity constant of 14.3 × 104 M−1 at 298 K. The thermodynamic analysis indicated that the interaction with IL-1β was spontaneous (∆G = −25 kJ/mol) and, when split into enthalpic and entropic contributions, the latter was more significant. Circular dichroism spectroscopy showed that piperine did not affect IL-1β secondary structure (~2%) and therefore its stability. The set of experimental data parameterized the computational biophysical approach. Through molecular docking, the binding site micro-environment was revealed to be composed mostly by non-polar amino acids. Furthermore, molecular dynamics, along with umbrella sampling, are in agreement with the thermodynamic parameters obtained by fluorescence assays and showed that large protein movements are not present in IL-1β, corroborating the circular dichroism data.

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