C8 having two peptide chains: C8β and C8αϒ. Binding of C8β with C5b67 complex causes conformational change in the C8 dimer such that hydrophobic domain of C8αϒ can insert into the interior of the phospholipid membrane.

TLS Online TPP Program

#Id: 1981

#Unit 3. Fundamental Processes

This structure is called a cap.

TLS Online TPP Program

#Id: 1982

#Unit 3. Fundamental Processes

After transcription initiation, Pol II is paused 30 nucleotides downstream from the initiation site, recruits of the capping enzymes.

TLS Online TPP Program

#Id: 1983

#Unit 3. Fundamental Processes

Capping is done by a dimeric nuclear enzyme which has two subunits and three functions

1. Guanylyl-transferase (GT)

2. Methyltransferase (MT)

TLS Online TPP Program

#Id: 1984

#Unit 3. Fundamental Processes

Structure of cap is

   

TLS Online TPP Program

#Id: 1985

#Unit 3. Fundamental Processes

Binding of the capping enzyme to the TFIIH mediated serine 5–phosphorylated CTD stimulates the activity of the enzyme.

TLS Online TPP Program

#Id: 1986

#Unit 3. Fundamental Processes

RNA polymerases I or III do not have a CTD so no capping is stimulated