Proteins: Secondary Structures

Proteins: Secondary Structures

1. a helix

   • tightly coiled rod of AAs
   • Hydrogen bond between 2/3rds of AAs
   • Carbonyl bond with amide 4 residues away
   • right handed (clockwise) or left handed (anti-clockwise).
     • right handed favoured for chirality and less chance steric hindereance from R-groups

2. Beta-pleated

   • hydrogen bond between carbonyl and amide residues
   • antiparallel
     • 1:1 AA bond ratio
     • R-groups facing out/in
   • Parallel
     • R-groups facing in/out
     • 2:1 AA bond ratio
   • Parallel and anti-parallel can exist in the same molecule

3. Reverse turns

   • Account for 1/3 of protein secondary structure
   • CO H-bond to NH 3 AA away

4. Secondary structure – refers to the formation and arrangement of regular & frequently occurring hydrogen-bond coordinatedsub-structures within the overall protein structure.

5. Omega-loop

6. All information for the formation of the secondary structure is stored within the primary sequence

7. Ribbon diagram shows all secondary structures clearly