DnaA is an ATP-binding protein.

The first stage in initiation is binding of the DnaA-ATP protein complex to the fully methylated oriC sequence.

This takes place in association with the inner membrane. DnaA is in the active form only when bound to ATP.

DnaA has intrinsic ATPase activity that hydrolyzes ATP to ADP and thus inactivates itself when the initiation stage ends.

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#Unit 1. Molecules and their Interaction Relevant to Biology

                                                                 Greek Key Motif

Made-up of beta-sheets

Four adjacent antiparallel strands linked by loops

Three anti-parallel beta sheets are connected 3 loops

The pattern is similar to ornamental pattern used I ancient Greece, therefore called as Greek Key motif

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#Unit 1. Molecules and their Interaction Relevant to Biology

                                                     Greek Key Motif

                                                        

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#Unit 1. Molecules and their Interaction Relevant to Biology

                                                           EF hand motif

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#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

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#Unit 1. Molecules and their Interaction Relevant to Biology

                                                             Omega loop

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#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