C alpha C and N C alpha C=0 and N C alpha C=0 and N C alpha N C and C alpha C N
ID: 56199 • Letter: C
Question
C alpha C and N C alpha C=0 and N C alpha C=0 and N C alpha N C and C alpha C N C alpha and N C Thr and/or Leu residues tend to disrupt an a helix when they occur next to each other in protein because: an amino acids like Thr is highly hydrophobic. covalent interactions may occur between the Thr side chains. electrostatic repulsion occurs between the Thr side chains. steric hindrance occurs between the bulky Thr side chains. the R group of Thr can form a hydrogen bond. An a helix would be destabilized most by: an electric dipole spanning several peptide bonds throughout the a helix. interactions between neighboring Asp and Arg residues. interactions between two adjacent hydrophobic Val residues. the presence of an Arg residue near the carboxyl terminus of the alpahaelix. the presence of two Lys residues near the amino terminus of the alpha helix. A sequence of amino acids in a certain protein is found to be -Ser-Gly-Pro-Gly-. The sequence is most prob
Explanation / Answer
* Leucine has a large aliphatic chain which is hydrophobic. The molecule is rigid and is not flexible to make a rotation across the axis due to its large side chain
* Threonine is high hydrophilic. Moreover, it has a reactive hydroxyl group. The C-C bond is free to rotate.
If present side by side, the two amino acids with differing characters disrupt the helix. Threonine has propensity to form beta strands, and leucine has propensity to form alpha helix.
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