The tertiary structure consists of a single polypeptide chain folded into a 3D shape stabilized by covalent and noncovalent interactions.
What characterizes quaternary protein structure?
The quaternary structure consists of multiple protein chains (subunits) assembled into a functional complex.
Difference between globular and fibrous proteins?
Globular proteins are water soluble with hydrophilic residues on the surface; fibrous proteins form insoluble fibers or sheets with tightly packed hydrophobic residues.
What are conjugated proteins?
Proteins that require non-protein components for function, such as glycoproteins, lipoproteins, metalloproteins, phosphoproteins, hemoproteins, and nucleoproteins.
Function and structure of myoglobin?
Myoglobin is a tertiary globular protein found in muscles that stores oxygen with a single polypeptide chain and a heme group.
Function and structure of hemoglobin?
Hemoglobin is a quaternary globular protein in red blood cells that transports oxygen; it has four polypeptide chains each with a heme group.
What causes sickle cell anemia at the molecular level?
A mutation replacing glutamate with valine at residue 6 in hemoglobin's beta chain creates a hydrophobic patch causing hemoglobin aggregation and sickled red blood cells.
How does electrophoresis separate proteins?
Electrophoresis separates proteins based on their charge and molecular weight by moving them through a porous gel under an electric field.
What is collagen and its structure?
Collagen is a tough, insoluble fibrous protein with a quaternary structure made of three tropocollagen strands stabilized by hydrogen bonds and covalent crosslinks.
Which amino acid allows close packing in tropocollagen?
The abundance of glycine residues every third position allows tight packing of the three collagen strands.
Diseases related to collagen defects?
Osteogenesis imperfecta (brittle bone disease) and scurvy (vitamin C deficiency affecting hydroxylation of proline) are related to collagen misfolding or deficiency.
What stabilizes the structure of hair?
Hair structure is stabilized by numerous disulfide bonds between cysteine residues in keratin proteins.
What stabilizes α-keratin packing?
Disulfide bonds forming between peptide chains stabilize the packing of α-keratin.
What stabilizes β-keratin strands?
Van der Waals interactions stabilize the packing of β-keratin strands.
What are chaperones in protein folding?
Chaperones are proteins or complexes that assist other proteins in folding correctly and prevent aggregation.
Why are prions considered infectious agents?
Prions induce normally folded proteins to misfold into β-sheet rich structures, propagating infectious misfolded proteins.
What diseases do prions cause?
Prions cause transmissible spongiform encephalopathies (TSEs), rare fatal brain disorders with spongy brain tissue.
What is protein degradation?
Protein degradation is the breakdown of proteins into amino acids by breaking peptide bonds, often via proteolysis.
Where does protein degradation occur in cells?
Protein degradation occurs in lysosomes and proteasomes within cells.
What causes protein denaturation?
Protein denaturation is caused by heat, mechanical agitation, detergents, organic solvents, pH changes, and high salt concentrations disrupting noncovalent interactions.