Proteomics Intro
Proteomics is the large-scale study of proteomes
Proteome = ALL the proteins present at a specific time
Why is Proteomics More Complicated Than Genomics?
Because proteome is CONSTANTLY CHANGING:
- Different proteins in brain vs. liver vs. skin
- Different proteins when you're a baby vs. adult
- Different proteins when you exercise, eat, sleep, or get sick
Why "Same Genes = Same Proteins" is WRONG?
Step 1: Not all genes are active
You have: ~20,000 genes total Each cell uses: Only ~11,000 genes This determines: What type of cell it is (brain, muscle, skin, etc.)
Step 2: Things get MORE complex because of:
One gene → can be "edited" into different versions
- Post-translational modifications (PTMs)
Proteins get chemically modified AFTER they're made Like buying a plain t-shirt, then adding patches, cutting it, dyeing it
- Protein-protein interactions (PPIs)
Proteins work in teams, not alone Different combinations = different functions
- Subcellular localization
WHERE the protein is located matters Same protein in the nucleus vs. membrane = different job
Levels Of Protein
Primary: The sequence of amino acids
Secondary:
- α-helix (alpha helix)
- β-sheet (beta sheet)
Tertiary Structure: The overall 3D shape of the ENTIRE protein chain
Held together by:
- Hydrogen bonds
- Ionic bonds
- Disulfide bridges (strong S-S bonds between cysteines)
- Hydrophobic interactions
Quaternary Structure: Multiple protein chains coming together
Primary (1°): ●—●—●—●—●—●—●—●—●
(linear chain)
Secondary (2°): ~~~●~~~ and ≋≋≋
(helix) (sheet)
Tertiary (3°): 🏀
(one chain folded into 3D shape)
Quaternary (4°): 🏀🏀
🏀🏀
(multiple chains together)
Chaperones help folding but don't determine folding
Chaperones increase during stress, That's why they're called "heat shock proteins"