QUESTION 6 Which of the following peptides is most likely an alpha helix? Arg-Ala-Tyr-Pro-Met-Gly-Val-Leu-Ser-Asp Glu-Ala-Tyr-Pro-Met-Gly-Val-Leu-Ser-Lys Glu-Ala-Tyr-Phe-Met-Gln-Val-Leu-Ser-Lys...

QUESTION 6 Which of the following peptides is most likely an alpha helix?

Arg-Ala-Tyr-Pro-Met-Gly-Val-Leu-Ser-Asp

Glu-Ala-Tyr-Pro-Met-Gly-Val-Leu-Ser-Lys

Glu-Ala-Tyr-Phe-Met-Gln-Val-Leu-Ser-Lys

Arg-Ala-Tyr-Phe-Met-Gln-Val-Leu-Ser-Asp

Expert Solution

Ans) The correct answer is "C"

Options A and B can straight away eliminated because the proline amino acid is not found in alpha helix because of the built in bend of proline which restricts the phi value to -60o (degrees).Proline disrupts alpha helix structure.Glycine is also not found in alpha helix because it has more conformational flexibility.

The amino acids which show high propensity to occur in alpha-helix are Methionine,Alanine,Leucine,Lysine,Glutamic acid,Glutamine,Arginine,Histidine. (Such propensities of each amino acids to occur in alpha-helix,turns,beta-pleated sheet can be found out by the use of amino acids propensity table).

Option D is incorrect because Arg has 1.21 propensity wheras Glu (in option C) has 1.59 propensity to occur in alpha-helix. Similarly,if we consider last amino acid i.e Asp (in option D) has 0.99 propensity wheras Lys (in option C) has 1.23 propensity.The rest of the amino acids are same in both options C and D. Thus,by this information we can conclude that the Option C peptide sequence is most likely to occur in alpha-helix.

gladiator answered 2 years ago

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