Use this signature sequence to answer the following questions: Use this signatur
ID: 71687 • Letter: U
Question
Use this signature sequence to answer the following questions:
Use this signature sequence to answer the following questions: Which position(s) has/have only positively charged amino acid functional groups pH 7? Which position has only negatively charged groups at pH 7? Which position(s) has/have an amino acid that is not found in alpha-helices? Which position(s) has/have an amino acid that could be detected by UV spectroscopy? Which position has an amino acid that is essential for the structure of collagen? Is this a signature sequence for collagen? Why or why not? What do the size of the letters indicate in the above figure?Explanation / Answer
a. The position 9 amino acid will have a positive charge at pH 7. The lysine amino acid will have a positive charge side chain at pH less than its pKa value (10.5).
b. The position 5 amino acid will have a negative charge ay pH7. The glutamic acid residue will have a negative charge side chain at pH more than its pKa value (4.2).
c. The position 2 amino acid is most likely not found in the alpha helix due to the presence of OH group in the side chain which hinders the formation of the helix. It poses a conformational instability to the structure.
d. The position 1 amino acid could be detected by the UV spectroscopy. The phenylalanine residue has a phenyl ring which will be resonance. This can absorb the UV light and emit the radiation to be detected at 280nm.
e. The positions 4 and 9 are important for the structure of collagen. 50% collagen is made up of lysine, glycine and proline.
f. Yes, it is a signature sequence of the collagen. Cross-links between two lysine residues at the C-terminus of one collagen molecule with two similar residues at the N-terminus of an adjacent molecule.
g. The size of the letters indicates that they can replace the respective amino acids without causing any change in the protein structure as they have similar side chain groups. The bigger the size the more probability of replacing the amino acid.
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