Protein Function and Structure

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Where do super secondary structures work?

function in the binding of small ligands and ions or in protein-DNA interactions

what diseases are prions responsible for?

kuru, Mad cow, Creutzfeldt-Jacob

What is denaturation?

loss of native conformation that produces loss of biologic activity denatured polypeptide chains aggregate and become insoluble due to interactions of exposed hydrophobic side chains

What are motifs?

secondary structures that have characteristic 3D shapes. Also called super secondary structures

What levels are disrupted by denaturing agents?

2nd,3rd,4th but NOT 1st

Explain primary structure of Proteins

Linear sequence of AA determines the secondary structure Mutations here often cause functional problems

Explain the secondary structure

arrangement of portions of a polypeptide chain stabilized by H-bonds 2 kinds- alpha helix & beta sheet

How are secreted proteins stabilized?

covalent disulfide bonds

what does proline do?

disrupts the alpha helix due to having an alpha amino group with no free H for H bonding aka stabilization

What are the major functions of Proteins

1. Structural Support 2. Movement 3. Signal Transduction 4. Binding 5. Molecule transport across membranes 6. Catalysis

Describe the denaturing agents

1. extreme changes in pH or ionic strength 2. Detergents 3. High temp 4. Heavy Metals

What connects AA together?

a peptide bond

What is a zinc-finger

a super secondary structure Zn+2 bound to 2 cys and his residues

what is a leucine zipper?

a super secondary structure leucine residues of 1 alpha helix interdigitate with those of another alpha helix to hold the proteins in a dimer

Why is sickle cell an example of a primary structure mutation

glutamate gets mutated to valine. Changes the charge (look at pbl for more on this)

Where are leucine zippers found?

in DNA-binding proteins like transcription factors

where are zinc fingers found?

in receptors that have a DNA-binding domain that interacts with lipid-soluble hormones

What are prions??

infectious proteins that cause normal neural proteins to change their secondary structure through contact usually make an alpha helix become a beta sheet form filamentous aggregates that are resistant to degradation by digestion or heat

What is an alpha helix

obviously helical side chains are located on the outside of the helix

what is a beta sheet

packing of beta strands

Explain the tertiary structure

the 3D folded structure of a polypeptide. also called the native conformation made up of many distinct structural and functional domains stabilized by side chain interactions Supersecondary motifs associate during folding to form tertiary structures

Explain Quaternary structure

the association of 2 or more tertiary structures dimers and tetramers are most common Can be held together by noncovalent interactions or by interchain disulfide bonds

What does G6PD deficiency have to due with denaturation?

the increased peroxide in RBC leads to the denaturing of hemoglobin and formation of Heinz bodies


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