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Protein Strctr
Protein Structure
| Question | Answer |
|---|---|
| 4 Molecular Organization Levels of Proteins | Primary Secondary Tertiary Quaternary |
| Functions of Proteins | Signaling, Transport, Catalysis, Movement, Structure, Regulation |
| Primary Structure | Sequence of Amino Acids. Known primary structure may be used to diagnose or study disease. |
| Amino Acids are joined by _________ bonds. | Peptide |
| How are peptide bonds formed? | N terminus to C terminus |
| Limitations of DNA sequencing | -Can't predict the disulfide bonds -Can't identify post-translational modifications |
| AA sequence is determined by: | sequencing the coding region of DNA |
| Secondary Structures | alpha-helix, beta-sheets, beta-bends |
| alpha-helix | -spiral, tightly packed structure -side chains extend outward |
| protein contents of alpha helices | -keratins are nearly entirely alpha-hilical -myoglobin contains only 8% alpha-helices |
| alpha helix hydrogen bonding | occurs between the carbonyl oxygen and the amide hydrogen of the backbone |
| disrupts alpha helix formation | -proline -large number of charged AA that form ionic bonds -large numbers of AA with bulky side chains |
| beta sheets | -appear pleated -hydrogen bonds are perpendicular to polypeptide backbone -parallel or anti-parallel |
| interchain bonds (beta sheets) | separate polypeptide chains |
| intrachain bonde (beta sheets) | single polypeptide |
| beta bends | -reverse turns -generally composed of 4 amino acids (often includes proline or glycine) |
| tertiary structure | -folding of domains and final arrangement of domains -Primary structure of polypeptide chain determines tertiary structure |
| Domains | fundamental functional 3D structural units of polypeptide |
| core domain (tertiary) | is built from a combination of motifs |
| The Four types of interactions that cooperate to stabilize tertiary structure of proteins | -Disulfide bonds -Hydrophobic interactions -Hydrogen bonds -Ionic interactions |
| Disulfide bond | formed by sulfhydryl groups (-SH) of two Cys residues |
| Hydrophobic interactions | -form between nonpolar side chains |
| process of folding | -process of folding in vivo often begins co-translationally from N-terminus |
| chaperones | -“heat shock proteins” - involved in various stages of folding -Keep protein unfolded -Increase the rate -Protect from unproductive interactions |
| examples of chaperones | GroEL, GroES |
| Denaturation | -unfolding and disorganizing of protein’s secondary and tertiary structures -done by heat, chemicals, and ions of heavy metals -can be reversible or irreversible |
| Quality control | misfolded proteins are tagged and degraded in the cell |
| Amyloids | -Accumulation of spontaneously aggregating proteins caused by misfolding -Associated with degenerative diseases like Alzheimer's disease. |
| Components of amyloid plaque in Alzheimer's | -amyloid precursor protein -neurofibrillary tangles in the brain caused by abnormal form of tau protein |
| Prion protein (PrP) | -Infectious protein produced in brain, resistant to proteolysis -causes transmissible spongiform encephalopathies (TSEs) -Creutzfeldt-Jakob disease in humans -Scrapie in sheep -Bovine spongiform encephalopathy “mad cow disease” in cattle |
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