Proteins 1: structure and function

What are the basic structures of proteins?

Primary, secondary, tertiary and quaternary structure

Primary structure basics?

Consists of alpha amino acids which determines primary structure

Form a peptide bond, in polypeptide amino acids are known as residues

Over 50 amino acids is protein

peptide bond is planar

What type of forces are found for protein structure?

Covalent bonds-primary

Hydrogen bonds-secondary

Hydrophobic/Van der waals-tertiary

Electrostatic forces in interior-tertiary

Van der Waals and electrostatic-quaternary

What are the two types of secondary protein structure?

Alpha helix-hydrogen bonds run parallel to helix axis

Beta sheet-hydrogen bonds run perpendicular to chain direction

Alpha helix structure?

alpha carbon backbone winds around axis

such that each carbonyl oxygen atom is hydrogen bonded to each amide nitrogen 4 residues closer to the C-terminus (COO)

N-terminus (NH3+)

What are the types of beta sheets?

anti-parallel and parallel

What do cysteine amino acids cause?

Cause formation of disulfide bonds

What is a tertiary domain?

Domain is smallest stable unit of tertiary structure

region of polypeptide chain that can fold into an autonomous stable tertiary structure

are stable as they are independent structural/functional groups

domains have switched between proteins-domain shuffling

How does haemoglobin’s quaternary structure affect its function?

T-state when unbound to oxygen and R-state when bound

produces curve where highest rate of oxygen association at lower pO2

Bohr effect where CO2 causes curve to shift right

Structure of collagen?

Three helical chains a triple gamma helix

Gly-x-y

Glycine is small so can fit in the centre of each helix

linked by hydrogen bonds

What is p53 structure?

consists of primary structure of transactivation domain 1 and 2, proline-rich region, DNA binding domain, NLS, tetramerisation domain, regulatory domain

forms a secondary, tertiary and quaternary structure