Purification of Human Hepatic Arginase and Its Manganese (II)-Dependent and pH-Dependent Interconversion between Active and Inactive Forms: A Possible pH-Sensing Function of the Enzyme on the Ornithine Cycle

1995 ◽  
Vol 320 (1) ◽  
pp. 24-34 ◽  
Author(s):  
N.J. Kuhn ◽  
S. Ward ◽  
M. Piponski ◽  
T.W. Young
Keyword(s):  
Ph Sensing ◽  
Ph Dependent

scholarly journals Mechanistic Basis of pH-Dependent 5-Flucytosine Resistance inAspergillus fumigatus

2018 ◽  
Vol 62 (6) ◽  
Author(s):  
Fabio Gsaller ◽  
Takanori Furukawa ◽  
Paul D. Carr ◽  
Bharat Rash ◽  
Christoph Jöchl ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Fungal Pathogens ◽  
Regulatory Protein ◽  
Transcriptional Regulators ◽  
Primary Factor ◽  
Ph Sensing ◽  
Content Type ◽  
Ph Dependent ◽  
Mechanistic Basis

ABSTRACTThe antifungal drug 5-flucytosine (5FC), a derivative of the nucleobase cytosine, is licensed for the treatment of fungal diseases; however, it is rarely used as a monotherapeutic to treatAspergillusinfection. Despite being potent against other fungal pathogens, 5FC has limited activity againstAspergillus fumigatuswhen standardin vitroassays are used to determine susceptibility. However, in modifiedin vitroassays where the pH is set to pH 5, the activity of 5FC increases significantly. Here we provide evidence thatfcyB, a gene that encodes a purine-cytosine permease orthologous to known 5FC importers, is downregulated at pH 7 and is the primary factor responsible for the low efficacy of 5FC at pH 7. We also uncover two transcriptional regulators that are responsible for the repression offcyBand, consequently, mediators of 5FC resistance, the CCAAT binding complex (CBC) and the pH regulatory protein PacC. We propose that the activity of 5FC might be enhanced by the perturbation of factors that repressfcyBexpression, such as PacC or other components of the pH-sensing machinery.

Solvent-controlled and solvent-dependent strategies for the synthesis of multicolor carbon dots for pH sensing and cell imaging

2019 ◽  
Vol 7 (31) ◽  
pp. 9709-9718 ◽  
Author(s):  
Jianliang Bai ◽  
Yusha Ma ◽  
Guojun Yuan ◽  
Xu Chen ◽  
Jing Mei ◽  
...  
Keyword(s):  
Carbon Dots ◽  
Cell Imaging ◽  
Ph Sensing ◽  
Ph Dependent

Solvent-controlled, pH-dependent and solvent-dependent strategies are proposed to obtain multicolor carbon dots using the same precursor.

scholarly journals Protonation of Individual Histidine Residues Is Not Required for the pH-Dependent Entry of West Nile Virus: Evaluation of the “Histidine Switch” Hypothesis

2009 ◽  
Vol 83 (23) ◽  
pp. 12631-12635 ◽  
Author(s):  
Steevenson Nelson ◽  
Subhajit Poddar ◽  
Tsai-Yu Lin ◽  
Theodore C. Pierson
Keyword(s):  
Life Cycle ◽  
West Nile Virus ◽  
Fusion Proteins ◽  
Viral Fusion ◽  
Ph Sensing ◽  
West Nile ◽  
Histidine Residues ◽  
E Protein ◽  
Viral Fusion Proteins ◽  
Ph Dependent

ABSTRACT Histidine residues have been hypothesized to function as sensors of environmental pH that can trigger the activity of viral fusion proteins. We investigated a requirement for histidine residues in the envelope (E) protein of West Nile virus during pH-dependent entry into cells. Each histidine was individually replaced with a nonionizable amino acid and tested functionally. In each instance, mutants capable of orchestrating pH-dependent infection were identified. These results do not support a requirement for any single histidine as a pH-sensing “switch,” and they suggest that additional features of the E protein are involved in triggering pH-dependent steps in the flavivirus life cycle.

scholarly journals Molecular interactions involved in proton-dependent gating in KcsA potassium channels

2013 ◽  
Vol 142 (6) ◽  
pp. 613-624 ◽  
Author(s):  
David J. Posson ◽  
Ameer N. Thompson ◽  
Jason G. McCoy ◽  
Crina M. Nimigean
Keyword(s):  
Amino Acids ◽  
Molecular Interactions ◽  
Ph Sensor ◽  
Model Parameters ◽  
Ph Sensing ◽  
Large Shift ◽  
X Ray Crystallography ◽  
Potassium Channel Kcsa ◽  
Ph Dependent ◽  
Open States

The bacterial potassium channel KcsA is gated open by the binding of protons to amino acids on the intracellular side of the channel. We have identified, via channel mutagenesis and x-ray crystallography, two pH-sensing amino acids and a set of nearby residues involved in molecular interactions that influence gating. We found that the minimal mutation of one histidine (H25) and one glutamate (E118) near the cytoplasmic gate completely abolished pH-dependent gating. Mutation of nearby residues either alone or in pairs altered the channel’s response to pH. In addition, mutations of certain pairs of residues dramatically increased the energy barriers between the closed and open states. We proposed a Monod–Wyman–Changeux model for proton binding and pH-dependent gating in KcsA, where H25 is a “strong” sensor displaying a large shift in pKa between closed and open states, and E118 is a “weak” pH sensor. Modifying model parameters that are involved in either the intrinsic gating equilibrium or the pKa values of the pH-sensing residues was sufficient to capture the effects of all mutations.

Multi-functional core-shell hybrid nanogels for pH-dependent magnetic manipulation, fluorescent pH-sensing, and drug delivery

Biomaterials ◽  
2011 ◽  
Vol 32 (36) ◽  
pp. 9876-9887 ◽  
Author(s):  
Weitai Wu ◽  
Jing Shen ◽  
Zheng Gai ◽  
Kunlun Hong ◽  
Probal Banerjee ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Core Shell ◽  
Ph Sensing ◽  
Magnetic Manipulation ◽  
Ph Dependent

scholarly journals A facile and green approach to prepare carbon dots with pH-dependent fluorescence for patterning and bioimaging

RSC Advances ◽  
2018 ◽  
Vol 8 (66) ◽  
pp. 38091-38099 ◽  
Author(s):  
Xin Guo ◽  
Yufu Zhu ◽  
Lei Zhou ◽  
Linna Zhang ◽  
Yucai You ◽  
...  
Keyword(s):  
Carbon Dots ◽  
Fruit Juices ◽  
Ph Sensing ◽  
Green Approach ◽  
Ph Dependent

Carbon dots prepared with the adoption of ubiquitous natural fruit juices as precursors have good applications in pH sensing, patterning and bioimaging.

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