lecture 16 - protein structure: cis vs trans peptide bonds

Question 1

for a trans peptide bond:

Answer 1

alphaC1 and alphaC2 are on opposite sides of the C-N peptide bond

Question 2

for a cis peptide bond:

Answer 2

aplhaC1 and alphaC2 are on the same side of the C-N peptide bond

Question 3

between cis or trans which is more energetically favourable? why?

Answer 3

• trans

- cis has extreme steric clashes

Question 4

excpetions to trans&raquo_space;> cis? why?

Answer 4

• in the case where the second amino acid is Pro
• the difference in energy between cis and trans is not so large
• cis is possible and is observed in ~5% of Pro