Measurement of Conformational Changes in the Structure of Transglutaminase on Binding Calcium Ions Using Optical Evanescent Dual Polarisation Interferometry

2007 ◽  
Vol 79 (8) ◽  
pp. 3023-3031 ◽  
Author(s):  
K. Karim ◽  
J. D. Taylor ◽  
D. C. Cullen ◽  
M. J. Swann ◽  
N. J. Freeman
Keyword(s):  
Conformational Changes ◽  
Calcium Ions ◽  
Dual Polarisation Interferometry

Influence of Calcium Ions on the Plant Cell Surface: Membrane Fusions and Conformational Changes

1974 ◽  
Vol 32 ◽  
pp. 154-155
Author(s):  
D. James Morré ◽  
Charles E. Bracker ◽  
William J. VanDerWoude
Keyword(s):  
Cell Wall ◽  
Cell Surface ◽  
Conformational Changes ◽  
Calcium Ions ◽  
Surface Membrane ◽  
Carboxyl Groups ◽  
Cross Linking ◽  
Ultrastructural Evidence ◽  
Glycine Max L ◽  
Wall Extensibility

Calcium ions in the concentration range 5-100 mM inhibit auxin-induced cell elongation and wall extensibility of plant stems. Inhibition of wall extensibility requires that the tissue be living; growth inhibition cannot be explained on the basis of cross-linking of carboxyl groups of cell wall uronides by calcium ions. In this study, ultrastructural evidence was sought for an interaction of calcium ions with some component other than the wall at the cell surface of soybean (Glycine max (L.) Merr.) hypocotyls.

scholarly journals Domain structure of human complement C4b extends with increasing NaCl concentration: implications for its regulatory mechanism

2016 ◽  
Vol 473 (23) ◽  
pp. 4473-4491 ◽  
Author(s):  
Ka Wai Fung ◽  
David W. Wright ◽  
Jayesh Gor ◽  
Marcus J. Swann ◽  
Stephen J. Perkins
Keyword(s):  
Crystal Structure ◽  
Domain Structure ◽  
Conformational Changes ◽  
Analytical Ultracentrifugation ◽  
Sedimentation Coefficient ◽  
Salt Bridge ◽  
X Ray ◽  
X Ray Scattering ◽  
Nacl Concentration ◽  
Dual Polarisation Interferometry

During the activation of complement C4 to C4b, the exposure of its thioester domain (TED) is crucial for the attachment of C4b to activator surfaces. In the C4b crystal structure, TED forms an Arg104–Glu1032 salt bridge to tether its neighbouring macroglobulin (MG1) domain. Here, we examined the C4b domain structure to test whether this salt bridge affects its conformation. Dual polarisation interferometry of C4b immobilised at a sensor surface showed that the maximum thickness of C4b increased by 0.46 nm with an increase in NaCl concentration from 50 to 175 mM NaCl. Analytical ultracentrifugation showed that the sedimentation coefficient s20,w of monomeric C4b of 8.41 S in 50 mM NaCl buffer decreased to 7.98 S in 137 mM NaCl buffer, indicating that C4b became more extended. Small angle X-ray scattering reported similar RG values of 4.89–4.90 nm for C4b in 137–250 mM NaCl. Atomistic scattering modelling of the C4b conformation showed that TED and the MG1 domain were separated by 4.7 nm in 137–250 mM NaCl and this is greater than that of 4.0 nm in the C4b crystal structure. Our data reveal that in low NaCl concentrations, both at surfaces and in solution, C4b forms compact TED–MG1 structures. In solution, physiologically relevant NaCl concentrations lead to the separation of the TED and MG1 domain, making C4b less capable of binding to its complement regulators. These conformational changes are similar to those seen previously for complement C3b, confirming the importance of this salt bridge for regulating both C4b and C3b.

scholarly journals Conformational Changes in Fibrous Elastin Due to Calcium Ions

1975 ◽  
Vol 51 (1) ◽  
pp. 73-78 ◽  
Author(s):  
William HORNEBECK ◽  
S. Miles PARTRIDGE
Keyword(s):  
Conformational Changes ◽  
Calcium Ions

scholarly journals Binding of calcium ions and SNAP-25 to the hexa EF-hand protein secretagogin

2006 ◽  
Vol 401 (1) ◽  
pp. 353-363 ◽  
Author(s):  
Annika Rogstam ◽  
Sara Linse ◽  
Anders Lindqvist ◽  
Peter James ◽  
Ludwig Wagner ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Calcium Ions ◽  
Tertiary Structure ◽  
Protein A ◽  
Hydrophobic Surface ◽  
Tumour Marker ◽  
Neuroendocrine Cells ◽  
Interacting Protein ◽  
Insulinoma Cell ◽  
Ef Hand

Secretagogin is a hexa EF-hand protein, which has been identified as a novel potential tumour marker. In the present study, we show that secretagogin binds four Ca2+ ions (log K1=7.1±0.4, log K2=4.7±0.6, log K3=3.6±0.7 and log K4=4.6±0.6 in physiological salt buffers) with a [Ca2+]0.5 of approx. 25 μM. The tertiary structure of secretagogin changes significantly upon Ca2+ binding, but not upon Mg2+ binding, and the amount of exposed hydrophobic surface in secretagogin increases upon Ca2+ binding, but not upon Mg2+ binding. These properties suggest that secretagogin belongs to the ‘sensor’ family of Ca2+-binding proteins. However, in contrast with the prototypical Ca2+ sensor calmodulin, which interacts with a very large number of proteins, secretagogin is significantly less promiscuous. Only one secretagogin-interacting protein was reproducibly identified from insulinoma cell lysates and from bovine and mouse brain homogenates. This protein was identified as SNAP-25 (25 kDa synaptosome-associated protein), a protein involved in Ca2+-induced exocytosis in neurons and in neuroendocrine cells. Kd was determined to be 1.2×10−7 M in the presence of Ca2+ and 1.5×10−6 M in the absence of Ca2+. The comparatively low Ca2+ affinity for secretagogin and the fact that it undergoes Ca2+-induced conformational changes and interacts with SNAP-25 raise the possibility that secretagogin may link Ca2+ signalling to exocytotic processes.

TMEM16A protein: calcium binding site and its activation mechanism

2021 ◽  
Vol 28 ◽  
Author(s):  
Wanying Ji ◽  
Donghong Shi ◽  
Sai Shi ◽  
Xiao Yang ◽  
Yafei Chen ◽  
...  
Keyword(s):  
Conformational Changes ◽  
Calcium Ions ◽  
Calcium Binding ◽  
Molecular Design ◽  
Chloride Ion ◽  
Activation Mechanism ◽  
Calcium Binding Site ◽  
Key Issues ◽  
Function Relationship ◽  
And Function

: TMEM16A mediates calcium-activated transmembrane flow of chloride ion and a variety of physiological functions. The binding of cytoplasmic calcium ions of TMEM16A and the consequent conformational changes of it are the key issues to explore the relationship between its structure and function. In recent years, researchers have explored this issue through electrophysiological experiment, structure resolving, molecular dynamic simulation and other methods. The structures of TMEM16 family members resolved by cryo-Electron microscopy (cryo-EM) and X-ray crystallization provide the primarily basis for the investigation of the molecular mechanism of TMEM16A. However, the binding and activation mechanism of calcium ions in TMEM16A are still unclear and controversial. This review discusses four Ca2+ sensing sites of TMEM16A and analyze activation properties of TMEM16A by them, which will help to understand the structure-function relationship of TMEM16A and throw light on the molecular design targeting TMEM16A channel.

scholarly journals Calcium ions and the conformation of glycoprotein IIIa that is essential fibrinogen binding to platelets: analysis by a new monoclonal anti-GP IIIa antibody, TM83

Blood ◽  
1989 ◽  
Vol 73 (6) ◽  
pp. 1552-1560
Author(s):  
N Yamamoto ◽  
H Kitagawa ◽  
K Yamamoto ◽  
K Tanoue ◽  
H Yamazaki
Keyword(s):  
Conformational Changes ◽  
Calcium Ions ◽  
Control Level ◽  
Human Platelets ◽  
Medium Ph ◽  
Activated Platelets ◽  
Fibrinogen Binding ◽  
Glycoprotein Iiia ◽  
Induced Aggregation ◽  
The Relationship

Using a newly developed murine monoclonal antibody (MoAb), TM83, against glycoprotein IIIa (GPIIIa) of human platelets, we have analyzed the relationship between platelet fibrinogen binding and conformational changes in GPIIIa under EDTA treatment. Crossed radioimmunoelectrophoresis demonstrated that TM83 reacted with only the GPIIb/IIIa complex but also with GPIIIa alone. TM83 dose-dependently inhibited both thrombin-induced aggregation and fibrinogen binding to activated platelets. 125I-TM83 bound to an average of 20,890 +/- 1,600 (mean +/- SE, n = 12) sites on a resting platelet, with Kd = 2.06 nmol/L in the presence of Ca2+. When platelets were incubated in 2 nmol/L EDTA-containing medium, pH 7.4, at 22 degrees C for 30 minutes, binding of TM83 decreased to 70% of the control level. The decreased binding was fully recovered to the control level when the platelets were resuspended in Ca2+-containing medium. These platelets retained their aggregability. In contrast, when platelets were incubated in 2 mmol/L EDTA-containing medium, pH 7.4, at 37 degrees C for 30 minutes, TM83 binding to the platelets markedly decreased to 7% of the control, which could only be recovered to 40% of the control by replacing the medium with calcium-containing medium; these platelets lacked thrombin- induced aggregability. These findings suggest that the epitope for TM83 may be located near the fibrinogen binding site on GPIIIa and that its conformation is dependent on Ca2+ ions.

scholarly journals Structural Changes of Sarco/Endoplasmic Reticulum Ca2+-ATPase Induced by Rutin Arachidonate: A Molecular Dynamics Study

Biomolecules ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 214
Author(s):  
Yoel Rodríguez ◽  
Magdaléna Májeková
Keyword(s):  
Molecular Dynamics ◽  
Endoplasmic Reticulum ◽  
Conformational Changes ◽  
Calcium Ions ◽  
Structural Changes ◽  
Acid Group ◽  
Bilayer Membrane ◽  
Salt Bridges ◽  
Drug Candidates ◽  
Dynamics Simulations

Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) maintains the level of calcium concentration in cells by pumping calcium ions from the cytoplasm to the lumen while undergoing substantial conformational changes, which can be stabilized or prevented by various compounds. Here we attempted to clarify the molecular mechanism of action of new inhibitor rutin arachidonate, one of the series of the acylated rutin derivatives. We performed molecular dynamics simulations of SERCA1a protein bound to rutin arachidonate positioned in a pure dipalmitoylphosphatidylcholine bilayer membrane. Our study predicted the molecular basis for the binding of rutin arachidonate towards SERCA1a in the vicinity of the binding site of calcium ions and near the location of the well-known inhibitor thapsigargin. The stable hydrogen bond between Glu771 and rutin arachidonate plays a key role in the binding. SERCA1a is kept in the E2 conformation preventing the formation of important salt bridges between the side chains of several residues, primarily Glu90 and Lys297. All in all, the structural changes induced by the binding of rutin arachidonate to SERCA1a may shift proton balance near the titrable residues Glu771 and Glu309 into neutral species, hence preventing the binding of calcium ions to the transmembrane binding sites and thus affecting calcium homeostasis. Our results could lead towards the design of new types of inhibitors, potential drug candidates for cancer treatment, which could be anchored to the transmembrane region of SERCA1a by a lipophilic fatty acid group.

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