In about half the polypeptides, the methionine at the terminus is removed by an aminopeptidase, which creates a new terminus from R2 (originally the second amino acid incorporated into the chain). When both steps are necessary, they occur sequentially. The removal reaction(s) occur rather rapidly when the nascent polypeptide chain has reached a length of 15 amino acids.

#Id: 7707

#Unit 1. Molecules and their Interaction Relevant to Biology

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. Molecules and their Interaction Relevant to Biology

                  Type l'β turn

#Id: 7709

#Unit 1. Molecules and their Interaction Relevant to Biology

                              Type II β turn

#Id: 7710

#Unit 1. Molecules and their Interaction Relevant to Biology

#Id: 7711

#Unit 1. Molecules and their Interaction Relevant to Biology

                                                                 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. Molecules and their Interaction Relevant to Biology

                                                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