Lecture 5 Web: pollev.com/ucibio Text: To: Type in:
OK. What does this all have to do with enzymes? Anfinsen’s experiment Took a protein (AP) & forced it to unfold - Protein lost activity Therefore:______________________________ Allowed protein to recover - Over time, activity returned Therefore:______________________________
What does a protein need in order to fold? Protein folding information contained in primary amino acid sequence! OK. But how does amino acid sequence “fold?”
Peptide bond is planar…
…but not bonds on either side!
Rotation of bonds around peptide bond
Peptide backbone rotation
“Folding” proteins Amino acids have different properties Different preferred Psi and Phi angles Bonds can rotate and pivot
Secondary structure 3D structure H-bonds between C=O & N-H C=O & N-H of peptide bonds Close together in primary structure
Folding into secondary structures Bond rotation causes secondary structure -helix -sheet Bends, Loops, Disordered
The -helix: Annotate Different parameters define -helix
-Sheet: Annotate
-Sheets Sheets can be twisted
Bends / Loops Bends or Loops: Important Structured/Unstructured
Tertiary structrue Bring secondary structure elements together Hydrophobic interactions important Unstructured regions important
The -helix Arrangement of side chains important
Tertiary structure
Tertiary structrue Take picture Upload to Dropbox assignment “Barrel structure”