Question

The secondary structure of a protein consists of a single long beta sheet. The outer edges of the beta sheet are composed of serine and proline amino acids. Describe the effect changing all the serine and proline amino acids to glycine would have on the secondary structure of the beta sheet. Also, predict the effect this change would have on the function of the protein in an aqueous environment.

Answer 1

@matt101 @e.mccormick

Answer 2

@matt101

Answer 3

@anonymous_user !

Answer 4

First consider the main properties of each of these amino acids. For serine, the R-group has an alcohol attached, making this amino acid polar. Proline is important because its unique structure allows "kinks" or sharp turns in the peptide chain. Glycine's R group is just a hydrogen atom and so it doesn't have too many special properties.

Keep in mind that to have a beta sheet, you need at least two beta strands. In this case, serine has its R group facing outwards, while proline is likely located at each bend in the beta sheet where the beta strands begin to run anti-parallel to one another. As a polar amino acid, serine is important for allowing the protein to remain dissolved in the aqueous solution. If you replace it with glycine, a nonpolar amino acid, the protein might begin to form large aggregates (groups) to create a hydrophobic environment that is more energetically stable. If all the proteins are grouped together, they probably won't be very good at doing what they're supposed to.

Proline is important for maintaining the shape of the beta sheet. If you replace it with glycine as well, the beta sheet will likely unfold because glycine cannot form angles tight enough to bring the individual beta strands together to form the hydrogen bonds required to make the beta sheet.

Hope that helps!