BIOC192 Lecture 5 - Elements of Protein Structure Flashcards
what is the primary structure of a protein?
the amino acid sequence of a protein
what is the secondary structure of a protein?
3D arrangement of a protein chain over a short stretch of adjacent amino acid residues
what is the tertiary structure of a protein?
3D structure of a complete protein chain
what is the quaternary structure of a protein?
interchain packing and structure for a protein that contains multiple protein chains
what are the main chain atoms in a protein?
1) N
2) alpha C
3) C’ (carbonyl carbon)
what is the range for bond angles?
+/- 180 degrees
what are the 3 main chain bond angles?
1) Ф = phi
2) Ψ = psi
3) ω = omega
what is the phi angle?
rotation angle around the N-C𝞪 (alpha carbon) bond
what is the psi angle?
rotation angle around the C𝞪 (alpha carbon)-C’ (carbonyl carbon) bond
what is the omega angle?
rotation angle around the peptide bond
what is phi-psi restrictions?
steric hinderance restricts the values of phi-psi angles
what is the result of phi-rotation restriction?
phi rotation can lead to O-O collision
what is the result of psi-rotation restriction?
psi rotation can lead to NH-NH collisions
what are the key properties of an 𝞪-helix?
- spiral is “right handed”
- side chains point out from the helix
- dipole present
- 3.6 residues in a 1 full turn at 5.4 Å per turn
- each residue goes up 1.5 Å
what are the key properties of a β structure?
- H-bonding occurs between adjacent chains
- often form a β sheet instead of 2 β-strands
- each strand may have up to 15 residues
- typically 2-10 strands per sheet
- side chains point above and below the sheet
- usually forms an alternating NP-P-NP-P stretch of residues
