553401
Description
Flashcards by Sophie Barrett, updated more than 1 year ago
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Created by Sophie Barrett
almost 11 years ago
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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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