Incorrect base pairing leads to dramatically lower rates of nucleotide addition as a result of a catalytically unfavorable alignment of these substrates. This is an example of kinetic proofreading, in which an enzyme favors catalysis using one of several possible substrates by dramatically increasing the rate of bond formation only when the correct substrate is present. 

#Id: 7707

#Unit 1. Structure and Function of Biomolecules

H bonding i-i+3, i+1 in BS while i+2 in below LHH which virtually not allowed region

for most of amino acid except Gly that is why Gly is most conserved in type II B turns

                                                                Type II β turn

#Id: 7708

#Unit 1. Structure and Function of Biomolecules

                  Type l'β turn

#Id: 7709

#Unit 1. Structure and Function of Biomolecules

                              Type II β turn

#Id: 7710

#Unit 1. Structure and Function of Biomolecules

#Id: 7711

#Unit 1. Structure and Function of Biomolecules

                                                                 α-Turn

Contains hydrophilic amino acids and protrudes outside the protein surface like a hook.

Consists of 5 amino acids, generally termed as i, i+1, i+2, i+3 and i+4

H-bond is seen between i and i+4 (First and Fifth residue)

The conformation of i+1, i+2 and i+3 are crucial and on the basis of this, they are classified into

9 groups

#Id: 7712

#Unit 1. Structure and Function of Biomolecules

                                                γ-Turn

Consists of 3 amino acids, generally termed as i, i + 1 and i + 2

H-bond is seen between i and i + 2 (First and Third residue)

The conformation of i + 1 is crucial and on the basis of this, they are classified into 2 groups

The dihedral angles of residue i + 1 are (70, -60) and (-70, 60) of the classical and inverse gamma turns