ubiquitin

Examples of ubiquitin in the following topics:

• Two-Hybrid Analysis

  • The split-ubiquitin system provides a method for overcoming this limitation.
  • In the split-ubiquitin system, two integral membrane proteins to be studied are fused to two different ubiquitin moieties: a C-terminal ubiquitin moiety ("Cub", residues 35–76) and an N-terminal ubiquitin moiety ("Nub", residues 1–34).
  • In addition to being fused to an integral membrane protein, the Cub moiety is also fused to a transcription factor (TF) that can be cleaved off by ubiquitin specific proteases.
  • Upon bait–prey interaction, Nub and Cub-moieties assemble, reconstituting the split-ubiquitin.
  • The reconstituted split-ubiquitin molecule is recognized by ubiquitin specific proteases, which cleave off the reporter protein, allowing it to induce the transcription of reporter genes.

• Regulating Protein Activity and Longevity

  • Proteins can be chemically modified with the addition of methyl, phosphate, acetyl, and ubiquitin groups.
  • The addition of an ubiquitin group to a protein marks that protein for degradation.
  • Ubiquitin acts like a flag indicating that the protein lifespan is complete.
  • One way to control gene expression is to alter the longevity of the protein: ubiquitination shortens a protein's lifespan.
  • Proteins with ubiquitin tags are marked for degradation within the proteasome.

• Proteolytic Degradation

  • This ubiquitin sequence is a modification to proteins that are targeted for degradation.
  • The recognition of this ubiquitin signal by the proteasome results in degradation of the protein into its amino acids, which are then recycled and reused for the synthesis of new proteins.
  • The protein is tagged with several ubiquitin signals that target the proteasome.

• Genomics and Proteomics

  • In addition, RNAs can be alternately spliced (cut and pasted to create novel combinations and novel proteins) and many proteins are modified after translation by processes such as proteolytic cleavage, phosphorylation, glycosylation, and ubiquitination.

• 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.