Post Translational Modifications

Sophie Barrett
Flashcards by Sophie Barrett, updated more than 1 year ago
Sophie Barrett
Created by Sophie Barrett over 7 years ago
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The Secretary and Non-Secretary Pathway

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Question Answer
Why are PTMs useful for the cell? Allows the cell to create proteins without them immediately eliciting a response in an incorrect location.
Which 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.
Protein following the Secretary Pathway are targeted to which organelle? The Rough Endoplasmic Reticulum (RER)
Which 3 main types of PTM occur there? 1) Cleavage (Proteolysis) 2) Glycosylation 3) Acetylation
How 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.
Describe Proteolysis Protein may be folded and bonds formed. Connecting polypeptide then cleaved. Remaining polypeptide very different from nascent protein.
Describe Glycosylation Addition of an N- or O-linked oligosaccharide (carbohydrate) in the ER.
List 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.
Describe Acetylation 80% of proteins are acetylated. Confers stabilty - non-acetylated proteins are rapidly degraded by proteases so have a shortened life-span.
Name 3 PTMs of the Non-Secretary Pathway 1) Small molecule modification. 2) Phosphorylation. 3) Metal Binding.
All 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.
Describe the formation of cAMP. Formed from ATP, catalysed by adenylyl cyclase (a trimeric G-protein).
Describe the structure of inactive PKA. Tetrameric form with: 2 regulatory subunits and 2 catalytic subunits
What are the 2 classes of Protein Kinases? 99% phosphorylate Serine or Threonine. 1% phosphorylate Tyrosine, so are called Tyrosine Kinases
What % of the human genome encodes Protein Kinases? 2% They are a very large family of important proteins.
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