A Tryptophan Rotamer Located in a Polar Environment Probes pH-Dependent Conformational Changes in Bovine β-Lactoglobulin A

2007 ◽  
Vol 111 (10) ◽  
pp. 2610-2620 ◽  
Author(s):  
Billie J. Harvey ◽  
Erin Bell ◽  
Lorenzo Brancaleon
Keyword(s):  
Conformational Changes ◽  
Polar Environment ◽  
Ph Dependent ◽  
Β Lactoglobulin

pH-Dependent Thermal Stability of Vibrio cholerae L-asparaginase

2019 ◽  
Vol 26 (10) ◽  
pp. 743-750 ◽  
Author(s):  
Remya Radha ◽  
Sathyanarayana N. Gummadi
Keyword(s):  
Vibrio Cholerae ◽  
Conformational Changes ◽  
Kinetic Studies ◽  
Structural Features ◽  
Structure Stability ◽  
Kcal Mole ◽  
Scanning Calorimetry ◽  
Wide Range ◽  
Ph Dependent ◽  
Ph Range

Background:pH is one of the decisive macromolecular properties of proteins that significantly affects enzyme structure, stability and reaction rate. Change in pH may protonate or deprotonate the side group of aminoacid residues in the protein, thereby resulting in changes in chemical and structural features. Hence studies on the kinetics of enzyme deactivation by pH are important for assessing the bio-functionality of industrial enzymes. L-asparaginase is one such important enzyme that has potent applications in cancer therapy and food industry.Objective:The objective of the study is to understand and analyze the influence of pH on deactivation and stability of Vibrio cholerae L-asparaginase.Methods:Kinetic studies were conducted to analyze the effect of pH on stability and deactivation of Vibrio cholerae L-asparaginase. Circular Dichroism (CD) and Differential Scanning Calorimetry (DSC) studies have been carried out to understand the pH-dependent conformational changes in the secondary structure of V. cholerae L-asparaginase.Results:The enzyme was found to be least stable at extreme acidic conditions (pH< 4.5) and exhibited a gradual increase in melting temperature from 40 to 81 °C within pH range of 4.0 to 7.0. Thermodynamic properties of protein were estimated and at pH 7.0 the protein exhibited ΔG37of 26.31 kcal mole-1, ΔH of 204.27 kcal mole-1 and ΔS of 574.06 cal mole-1 K-1.Conclusion:The stability and thermodynamic analysis revealed that V. cholerae L-asparaginase was highly stable over a wide range of pH, with the highest stability in the pH range of 5.0–7.0.

scholarly journals Correlation of membrane protein conformational and functional dynamics

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Raghavendar Reddy Sanganna Gari ◽  
Joel José Montalvo‐Acosta ◽  
George R. Heath ◽  
Yining Jiang ◽  
Xiaolong Gao ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Conformational Changes ◽  
Single Channel ◽  
Conformational Dynamics ◽  
Md Simulations ◽  
High Temporal Resolution ◽  
Dependent Manner ◽  
Functional Dynamics ◽  
Ph Dependent ◽  
Open States

AbstractConformational changes in ion channels lead to gating of an ion-conductive pore. Ion flux has been measured with high temporal resolution by single-channel electrophysiology for decades. However, correlation between functional and conformational dynamics remained difficult, lacking experimental techniques to monitor sub-millisecond conformational changes. Here, we use the outer membrane protein G (OmpG) as a model system where loop-6 opens and closes the β-barrel pore like a lid in a pH-dependent manner. Functionally, single-channel electrophysiology shows that while closed states are favored at acidic pH and open states are favored at physiological pH, both states coexist and rapidly interchange in all conditions. Using HS-AFM height spectroscopy (HS-AFM-HS), we monitor sub-millisecond loop-6 conformational dynamics, and compare them to the functional dynamics from single-channel recordings, while MD simulations provide atomistic details and energy landscapes of the pH-dependent loop-6 fluctuations. HS-AFM-HS offers new opportunities to analyze conformational dynamics at timescales of domain and loop fluctuations.

pH-Dependent Aggregation and Disaggregation of Native β-Lactoglobulin in Low Salt

Langmuir ◽  
2013 ◽  
Vol 29 (14) ◽  
pp. 4584-4593 ◽  
Author(s):  
Yunfeng Yan ◽  
Daniel Seeman ◽  
Bingqian Zheng ◽  
Ebru Kizilay ◽  
Yisheng Xu ◽  
...  
Keyword(s):  
Low Salt ◽  
Aggregation And Disaggregation ◽  
Ph Dependent ◽  
Β Lactoglobulin

scholarly journals pH-Dependent Conformational Changes in Proteins and Their Effect on Experimental pKas: The Case of Nitrophorin 4

2012 ◽  
Vol 8 (11) ◽  
pp. e1002761 ◽  
Author(s):  
Natali V. Di Russo ◽  
Dario A. Estrin ◽  
Marcelo A. Martí ◽  
Adrian E. Roitberg
Keyword(s):  
Conformational Changes ◽  
Nitrophorin 4 ◽  
Ph Dependent

scholarly journals pH-Dependent Conformational Changes of Concanavalin A

1971 ◽  
Vol 68 (9) ◽  
pp. 2173-2176 ◽  
Author(s):  
R. Zand ◽  
B. B. L. Agrawal ◽  
I. J. Goldstein
Keyword(s):  
Conformational Changes ◽  
Concanavalin A ◽  
Ph Dependent

The pH-Dependent Interaction of Cinnamomin with Lipid Membranes Investigated by Fluorescence Methods

2000 ◽  
Vol 381 (7) ◽  
pp. 567-573 ◽  
Author(s):  
Rong-gui Hu ◽  
Shuang Tang ◽  
Wang-yi Liu
Keyword(s):  
Conformational Changes ◽  
Lipid Membranes ◽  
Type Ii ◽  
Ans Binding ◽  
Tryptophan Residues ◽  
New Type ◽  
Small Unilamellar Vesicles ◽  
Ph Dependent ◽  
Endocytic Vesicles

Abstract Cinnamomin, a new type II ribosomeinactivating protein (RIP), was found to be able to induce the release of calcein loaded in lecithin small unilamellar vesicles and the fusion or aggregation of the lecithin liposomes. Such induction could be promoted several fold by a pH 5.0 environment, a condition similar to that in endocytic vesicles. Lowering the pH from 7.5 to 5.0 evoked conformational changes of cinnamomin and unmasked its hydrophobic areas, including the exposure of 1-anilino-8-naphthalenesulfonate (1,8-ANS) binding sites of the molecule. Some tryptophan residues with affinity to acrylamide were demonstrated to participate in the lipidprotein interaction. The pH dependent fusogenicity of type II RIP might suggest its in vivo function as a fusogen to exert its cytotoxicity.

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