Protein Hormone Production
  1. Transcription of nuclear gene, including introns and exons, into heteronuclear mRNA
  2. Excision of introns and modification of the transcript by capping of the 5' end and addition of the poly-A tail to the 3' end to generate mature mRNA.
  3. Binding of mRNA to ribosomes on the endoplasmic reticulum.
  4. Translation of mRNA into precursor protein, often with a leader sequence that inserts through the ER membrane with the help of a docking protein.
  5. Clipping of the leader sequence, protein folding, and formation of -S-S- bridges.
  6. Movement to the Golgi Apparatus where carbohydrate additions and modifications occur.
  7. Movement up the Golgi stack toward the plasma membrane as limited proteolysis, further protein folding and condensation occur (e.g., multimer formation)
  8. Packaging of the proteins in granules ready for exocytosis
- As the modification processes continue in the granules, protein ages in the granules. It has been found that the freshest, most biologically active, protein is secreted first if an impulse to exocytose the granules is received: last made = first out.