Protein processing Flashcards
What is Constitutive Secretion?
A continuous process
Proteins are packaged into vesicles and secreted by exocytosis
What is Regulated Secretion?
Proteins are packaged into a vesicle, but released in response to a signal
What modifications can occur in the ER?
Signal cleavage
N linked glycosylation
Disulphide bond formation
What modifications can occur in the golgi?
O linked glycosylation
Modification of N linked oligosaccharides
Where does Proteolytic removal of the N-terminal signal occur?
Early on in the ER
Where does further processing of proteins occur?
In the Golgi body
How is mature insulin formed?
Preproinsulin (contains Signal sequence, A, B and C peptides) cleaved by signal peptidase (Signal sequence removed)
Proinsulin (A, B and C peptides) C cleaved by endopeptidases
Insulin (Has A and B peptides) Has 2 disulphide bridges
What do proteins that can enter the nucleus usually contain?
Nuclear Localisation Sequence (NLS).
What aids the transport of proteins into the nucleus?
Importin
How does Penicillin work as an antibiotic?
Inhibits transpeptidase enzyme that forms cross-links in cell wall. Osmotic pressure causes cell lysis
How does Rifampicin work as an antibiotic?
Binds to bacterial RNA Polymerase preventing transcription.
How does tetracycline work as an antibiotic?
Competes with tRNA at A site of bacterial ribosome.
How does Methotrexate work in cancer therapy?
Impairs the synthesis of tetrahydrofolate, which is essential for DNA synthesis, from folic acid. Competitively inhibits dihydrofolate reductase (DHFR)
How can bacteria become resistant to antibiotics?
High rate of division Decreased influx Increased efflux Increased transcription of target Altered target
