1.

Which of the following is not correct about the α-Helices?(a) An α-helix has a main chain backbone conformation that resembles a corkscrew(b) Nearly all known α-helices are right handed, exhibiting a leftward spiral form(c) Nearly all known α-helices are right handed, exhibiting a rightward spiral form(d) In right handed helix, there are 3.6 amino acids per helical turnI have been asked this question during an internship interview.My question is from Protein Structure Basics topic in section Structural Bioinformatics of Bioinformatics

Answer»

Correct choice is (b) NEARLY all known α-helices are right handed, exhibiting a leftward spiral form

Easiest explanation: The STRUCTURE is stabilized by HYDROGEN bonds formed between the main CHAIN atoms of residues i and i + 4. The hydrogen bonds are nearly parallel with the helical axis. The average φ and ψ angles are 60◦ and 45◦, respectively, and are distributed in a narrowly DEFINED region in the lower left region of a Ramachandran plot.



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