Building a Proteome: Modification and Degradation Flashcards
Lecture 5
What is covalent modification?
addition of a functional group
List 4 examples of covalent modification.
Ubiquination
Acetylation
Phosphorylation
Glycosylation
What does a protease do?
cleaves peptide bonds
How is proinsulin processed?
A protease cleaves peptide bonds, leaving just insulin.
Which amino acid do phosphate groups get added to (only evidenced by figure)?
Serine
Which amino acid do acetyl groups get added to? (evidenced by example)
Lysine
What are isoforms? Why do they exist?
Peptides with the same amino acid sequence, but different functional groups (after covalent modifications). They help increase molecular diversity, helping cells to regulate processes.
Which amino acids can receive phosphate groups? What quality allows them to do so?
Serine, Threonine, and Tyrosine
Only amino acids with OH groups.
Does phosphorylation turn a protein on or off?
Trick question! Can do either, depending on the identity of the protein in question.
What does a protein kinase do?
Removes a phosphate group from ATP, adding it to a side chain (either serine, threonine, or tyrosine)
What does a protein phosphatase do?
Cleaves inorganic phosphate from a side chain
What are the three polypeptide degradation methods?
Via the proteosome
Via the lysosome
Via autophagosomes
What is a proteosome and what does it do?
Large protein unit comprised of multiple; looks like a hollow tube; core receives 2 caps when operating
Degrades (chops up) polypeptides
What determines which mechanism is used to degrade a protein?
The protein in question
What must happen before a proteosome degrades a protein?
Ubiquination; ubiquitin must target a protein for destruction