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Related Concept Videos

Acid and Bases: Ka, pKa, and Relative Strengths02:35

Acid and Bases: Ka, pKa, and Relative Strengths

This lesson delves into a critical aspect of the relative strengths of acids and bases. The strength of an acid is evaluated by the acid dissociation into its conjugate base and a hydronium ion in water. The complete dissociation of a strong acid is confirmed with a very high concentration of hydronium ions. As a result, an incomplete dissociation process affirms a weak acid. Therefore, the equilibrium is in the forward direction for strong acids and backward for weak acids in these reactions.
Protein Kinases and Phosphatases02:54

Protein Kinases and Phosphatases

Proteins undergo chemical modifications that trigger changes in the charge, structure, and conformation of the proteins. Phosphorylation, acetylation, glycosylation, nitrosylation, ubiquitination, lipidation, methylation, and proteolysis are various protein modifications that regulate protein activity. Such modifications are usually enzyme-driven.
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...
Protein Kinases and Phosphatases02:54

Protein Kinases and Phosphatases

Proteins undergo chemical modifications that trigger changes in the charge, structure, and conformation of the proteins. Phosphorylation, acetylation, glycosylation, nitrosylation, ubiquitination, lipidation, methylation, and proteolysis are various protein modifications that regulate protein activity. Such modifications are usually enzyme-driven.
Protein kinases
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Factors Affecting Dissolution: Drug pKa, Lipophilicity and GI pH01:21

Factors Affecting Dissolution: Drug pKa, Lipophilicity and GI pH

Drug absorption within the gastrointestinal (GI) tract is a complex process influenced by several critical factors, including the site pH, the drug's dissociation constant (pKa), and the drug's lipophilicity. The GI tract exhibits a pH gradient, with an acidic environment in the stomach and a more alkaline environment in the small intestine. This pH variation directly affects the ionization state of drugs.
A drug's pKa and the pH of the gastrointestinal (GI) tract play crucial roles in drug...
Position of Equilibrium in Acid-Base Reactions02:05

Position of Equilibrium in Acid-Base Reactions

In any solution, the value of pKa indicates whether an acid is completely dissociated or not. A negative pKa corresponds to a stronger acid, whereas a positive pKa corresponds to a weaker acid. Consider the reaction between ammonia and an ethoxide ion. In this reaction, ethanol with a pKa of 15.9 is a stronger acid than ammonia with a pKa of 38. Recall that the strong acid forms a weak conjugate base, and a weak acid forms a strong conjugate base. Hence, the ethoxide ion is a weak base.
Nonlinear Pharmacokinetics: Overview01:19

Nonlinear Pharmacokinetics: Overview

Nonlinear or dose-dependent pharmacokinetics is a phenomenon that occurs when the pharmacokinetic parameters of certain drugs deviate from linear pharmacokinetics at higher doses. These drugs do not follow the expected first-order kinetics, where the rate of drug elimination is directly proportional to the drug concentration. Instead, they exhibit a nonlinear relationship, which can be attributed to several factors.
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Live-imaging of PKC Translocation in Sf9 Cells and in Aplysia Sensory Neurons
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PKA: lessons learned after twenty years.

Susan S Taylor1, Ping Zhang, Jon M Steichen

  • 1Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093-0654, USA. staylor@ucsd.edu

Biochimica Et Biophysica Acta
|March 29, 2013
PubMed
Summary
This summary is machine-generated.

Protein kinases function as molecular switches, with their activity regulated by dynamic assembly of a hydrophobic spine. Understanding these dynamic complexes is key to PKA signaling and drug development.

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Area of Science:

  • Biochemistry
  • Structural Biology
  • Molecular Pharmacology

Background:

  • The first protein kinase structure revealed a conserved fold and active site organization.
  • Eukaryotic protein kinases (EPKs) are crucial drug targets, second only to GPCRs.
  • Protein kinase A (PKA) serves as a prototype for understanding kinase catalysis and regulation.

Purpose of the Study:

  • To elucidate the structural basis of protein kinase activation and regulation.
  • To highlight the role of the hydrophobic spine in active kinase conformation.
  • To understand the assembly and function of PKA holoenzymes and their localization.

Main Methods:

  • X-ray crystallography of PKA catalytic (C) and regulatory (R) subunits, and holoenzyme complexes.
  • Comparative structural analysis of active and inactive kinases.
  • Investigation of PKA holoenzyme localization using A Kinase Anchoring Proteins (AKAPs).

Main Results:

  • Discovery of a conserved hydrophobic spine architecture characteristic of active kinases.
  • Identification of dynamic assembly of the regulatory spine as a defining feature of protein kinases.
  • Elucidation of PKA holoenzyme structure (R2:C2) and its regulation by cAMP and AKAPs.

Conclusions:

  • Protein kinases function as dynamic molecular switches, analogous to G-proteins.
  • Understanding the structural dynamics of kinase complexes is essential for comprehending PKA signaling.
  • Further research into these dynamic macromolecular complexes is critical for therapeutic advancements.