scrunching model -proposes that DNA downstream from the stationary, promoter-bound, polymerase is unwound and pulled into the enzyme. The DNA thus accumulated within the enzyme is accommodated as single-stranded bulges.

#Id: 7699

#Unit 1. Molecules and their Interaction Relevant to Biology

                                                           EF hand motif

#Id: 7701

#Unit 1. Molecules and their Interaction Relevant to Biology

                                                                  Omega loop

Beginning and end of the loop come together

The shape appears similar to Greek Capital Omega

Compact Globular structure

No regular repeating pattern of hydrogen bonds

Side chains pack into the center of the loop

Omega loops have specific functions like

Omega loop from two proteins interact with each other to form dimers

Phosphate binding loop of nucleotide proteins

#Id: 7702

#Unit 1. Molecules and their Interaction Relevant to Biology

                                                             Omega loop

#Id: 7704

#Unit 1. Molecules and their Interaction Relevant to Biology

                                                           Loops and Turn

Small loops with regular hydrogen bond pattern and specific dihedral angles are termed as turns

#Id: 7705

#Unit 1. Molecules and their Interaction Relevant to Biology

                                                               β-turns

Most common turns, also termed as ẞ-bends, tight turns, reverse turns, generally connects

β-sheets.

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

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

H-bond is seen between i and i+3 (First and Fourth residue)

#Id: 7706

#Unit 1. Molecules and their Interaction Relevant to Biology

                                                                                                Type I β turn