Sites of phosphorylation on the CTD serve as a recognition or anchor point for other proteins to dock with the polymerase. The capping enzyme (guanylyl transferase), which adds the G residue to the 5' end of newly synthesized mRNA, binds to CTD phosphorylated at serine 5, the first phosphorylation event catalyzed by TFIIH. 

P-TEFb leads to recruitment of a set of proteins called SCAFs to the CTD, and they in turn bind to splicing factors. This may be a means of coordinating transcription and splicing.

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#Unit 1. Molecules and their Interaction Relevant to Biology

                                                               Helix-turn-Helix

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#Unit 1. Molecules and their Interaction Relevant to Biology

                                                       Zinc Finger Motif

Zinc atom stabilizes the structure/fold by coordination bonds

Each motif contains about 30-50 amino acids

Contains regular patterns of Cys / His, which coordinate with Zinc atom

Contains one helix and two small anti-parallel beta sheets in each finger

Zinc holds helix and beta-sheets together

Helix binds to DNA

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#Unit 1. Molecules and their Interaction Relevant to Biology

                                         Zinc Finger Motif

 


#Id: 7690

#Unit 1. Molecules and their Interaction Relevant to Biology

                                                                  bab Motif

Two beta strands are connected by a long region containing a helix

These beta strands form parallel beta-sheets

The loop regions connecting sheet and helix can have different length

The helix axis is generally parallel to beta-sheets

Three secondary structures are stabilized by hydrophobic interactions


#Id: 7691

#Unit 1. Molecules and their Interaction Relevant to Biology

                                             bab Motif

These motifs are generally found in right handed helix above the plane of the beta sheet

Almost all the proteins containing parallel beta sheets have this motif. 

The helix is generally not seen below the plane of beta sheets                                           

#Id: 7692

#Unit 1. Molecules and their Interaction Relevant to Biology

                                                  bab Motif