phosphorylation

Examples of phosphorylation in the following topics:

• Fermentation Without Substrate-Level Phosphorylation

  • Even in the presence of abundant oxygen, yeast cells greatly prefer fermentation to oxidative phosphorylation, as long as sugars are readily available for consumption (a phenomenon known as the Crabtree effect).
  • Fermentation is important in anaerobic conditions when there is no oxidative phosphorylation to maintain the production of ATP (adenosine triphosphate) by glycolysis.
  • For example, even in the presence of abundant oxygen, yeast cells greatly prefer fermentation to oxidative phosphorylation, as long as sugars are readily available for consumption (a phenomenon known as the Crabtree effect).

• Two-Component Regulatory Systems

  • Signal transduction occurs through the transfer of phosphoryl groups from adenosine triphosphate (ATP) to a specific histidine residue in the histidine kinases (HK).
  • The level of phosphorylation of the response regulator controls its activity.
  • Some HK are bifunctional, catalysing both the phosphorylation and dephosphorylation of their cognate RR.
  • Here a hybrid HK autophosphorylates and then transfers the phosphoryl group to an internal receiver domain, rather than to a separate RR protein.
  • The phosphoryl group is then shuttled to histidine phosphotransferase (HPT) and subsequently to a terminal RR, which can evoke the desired response.

• Respiration and Proton Motive Force

  • The products of the Krebs cycle include energy in the form of ATP (via substrate level phosphorylation), NADH, and FADH2.
  • The initial phosphorylation of glucose is required to destabilize the molecule for cleavage into two pyruvate.
  • With the help of phosphofructokinase, an additional ATP can be used to turn phosphorylate fructose 6-phosphate into fructose 1, 6-diphosphate.
  • Fructose 1, 6-diphosphate then splits into two phosphorylated molecules with three carbon chains that later degrades into pyruvate.
  • The overall process of creating energy in this fashion is termed oxidative phosphorylation.

• Toll-Like Receptors

  • IRAK kinases then phosphorylate and activate the protein TRAF6, which in turn polyubiquinates the protein TAK1, as well as itself in order to facilitate binding to IKKβ.
  • On binding, TAK1 phosphorylates IKKβ, which then phosphorylates IκB causing its degradation and allowing NFκB to diffuse into the cell nucleus and activate transcription.
  • The TRIF/TBK1 signaling complex phosphorylates IRF3 allowing its translocation into the nucleus and production of Type I interferons.

• Acetyl CoA and the Citric Acid Cycle

  • The NADH generated by the TCA cycle is fed into the oxidative phosphorylation pathway.
  • The NADH and QH2 that is generated by the citric acid cycle is used by the oxidative phosphorylation pathway to generate energy-rich adenosine triphosphate (ATP).

• Cytomegalovirus Infections

  • Its antiviral activity requires phosphorylation by the HCMV protein kinase, pUL97.
  • The second drug, Cidofovir (CDV), is a nucleotide analogue, which is already phosphorylated and thus active.

• Proton Reduction

  • This potential energy is used for the synthesis of ATP by phosphorylation.
  • The overall process of creating energy in this fashion is termed oxidative phosphorylation.
  • Instead, it only uses substrate-level phosphorylation to produce ATP.

• Chemotaxis

  • CheA in turn transfers phosphoryl groups to conserved aspartate residues in the response regulators CheB and CheY [note: CheA is a histidine kinase and it does not actively transfer the phosphoryl group.
  • The response regulator CheB takes the phosphoryl group from CheA].

• Interferons

  • In this pathway, JAKs associate with IFN receptors and, following receptor engagement with IFN, phosphorylate both STAT1 and STAT2.
  • PI3K activates P70-S6 Kinase 1, an enzyme that increases protein synthesis and cell proliferation; phosphorylates of ribosomal protein s6, which is involved in protein synthesis; and phosphorylates a translational repressor protein called eukaryotic translation-initiation factor 4E-binding protein 1 (EIF4EBP1) in order to deactivate it.

• Proteomics

  • Not only does the translation from mRNA cause differences, but many proteins are also subjected to a wide variety of chemical modifications after translation which are critical to the protein's function such as phosphorylation, ubiquitination, methylation, acetylation, glycosylation, oxidation, and nitrosylation.
  • For example, some proteins are not active until they become phosphorylated.
  • For example, there are antibodies that only recognize certain proteins when they are tyrosine-phosphorylated, known as phospho-specific antibodies.