Flashcards
Post Translational Modifications
Cards in this deck (15)
- 1Why are PTMs useful for the cell?Allows the cell to create proteins without them immediately eliciting a response in an incorrect location.
- 2Which 2 pathways are used in eukaryotes for modifying proteins?1) The Secretary Pathway e.g. for hormone, transmitters, receptors.
2) The Non-Secretary Pathways for e.g. enzymes, signalling molecules. - 3Protein following the Secretary Pathway are targeted to which organelle?The Rough Endoplasmic Reticulum (RER)
- 4Which 3 main types of PTM occur there?1) Cleavage (Proteolysis)
2) Glycosylation
3) Acetylation - 5How is the nascent protein targeted to the RER?Nascent protein has ER Signal Sequence (16-30 amino acids long with 1+ positively charged). Recognised by a membrane channel on the RER.
- 6Describe ProteolysisProtein may be folded and bonds formed. Connecting polypeptide then cleaved. Remaining polypeptide very different from nascent protein.
- 7Describe GlycosylationAddition of an N- or O-linked oligosaccharide (carbohydrate) in the ER.
- 8List some possible effects of Glycosylation as a PTM.May promote stability, folding or cell-cell adhesion.
Protects protein parts which are external to membrane from proteolytic enzymes. - 9Describe Acetylation80% of proteins are acetylated.
Confers stabilty - non-acetylated proteins are rapidly degraded by proteases so have a shortened life-span. - 10Name 3 PTMs of the Non-Secretary Pathway1) Small molecule modification.
2) Phosphorylation.
3) Metal Binding. - 11All these PTMs of the Non-Secretary Pathway are Allosteric Changes - what does this mean?A change in the proteins tertiary or quaternary structure induced by the binding of regulatory molecules/substrates that results in a transition to a state with different activity.
- 12Describe the formation of cAMP.Formed from ATP, catalysed by adenylyl cyclase (a trimeric G-protein).
- 13Describe the structure of inactive PKA.Tetrameric form with:
2 regulatory subunits
and
2 catalytic subunits - 14What are the 2 classes of Protein Kinases?99% phosphorylate Serine or Threonine.
1% phosphorylate Tyrosine, so are called Tyrosine Kinases - 15What % of the human genome encodes Protein Kinases?2%
They are a very large family of important proteins.
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- The Secretary and Non-Secretary Pathway
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- Sophie Barrett
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