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Protein Strctr

Protein Structure

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
Created by: 1526302205