Shown below are two cartoon views of the small globular protein StrepG inwhich an α helix is packed against a four-strand β sheet. The sheet is madeup of two “β-hairpins” (a β-hairpin is a “β-turn-β” structure). Refer to theimages and answer the questions that follow: (a) Identify the locations of the N- and C-termini of StrepG.(b) Indicate the orientation of the helical macrodipole, showing the (δ+)and (δ-) ends of the macrodipole.(c) How many residues are in the helix?(d) Do you predict that the α helix and β sheet are amphiphilic or not?Briefly explain.(e) The following two peptides are part of the primary sequence of StrepG.Based on your answer to part (d), which one is more likely to correspondto the α helix? Which is most likely to be part of a β-hairpin? Explainyour choice.Peptide #1: DAATAEKVFKQYAND or Peptide #2: VDGEWTYDDATKTFTV
Proteins
We generally tend to think of proteins only from a dietary lens, as a component of what we eat. However, they are among the most important and abundant organic macromolecules in the human body, with diverse structures and functions. Every cell contains thousands and thousands of proteins, each with specific functions. Some help in the formation of cellular membrane or walls, some help the cell to move, others act as messages or signals and flow seamlessly from one cell to another, carrying information.
Protein Expression
The method by which living organisms synthesize proteins and further modify and regulate them is called protein expression. Protein expression plays a significant role in several types of research and is highly utilized in molecular biology, biochemistry, and protein research laboratories.
Shown below are two cartoon views of the small globular protein StrepG in
which an α helix is packed against a four-strand β sheet. The sheet is made
up of two “β-hairpins” (a β-hairpin is a “β-turn-β” structure). Refer to the
images and answer the questions that follow: (a) Identify the locations of the N- and C-termini of StrepG.
(b) Indicate the orientation of the helical macrodipole, showing the (δ+)
and (δ-) ends of the macrodipole.
(c) How many residues are in the helix?
(d) Do you predict that the α helix and β sheet are amphiphilic or not?
Briefly explain.
(e) The following two peptides are part of the primary sequence of StrepG.
Based on your answer to part (d), which one is more likely to correspond
to the α helix? Which is most likely to be part of a β-hairpin? Explain
your choice.
Peptide #1: DAATAEKVFKQYAND or Peptide #2: VDGEWTYDDATKTFTV
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