• The 5'-end is capped with a 7-methylguanine
  • The cap protects against ribonucleases, and assists binding to the ribosome

• A polyA "tail" of 70-150 As is attached to the 3'-end
  • In prokaryotes the tail stimulates degradation; in eukaryotes, the opposite

Guanylyl Transferase (1cko)	Polyadenylase with ADP and ATP (1fa0)

Transfer RNA undergoes processings as well:

The 5'-end is processed by RNase P, a species universal in all three forms of life:

RNase P (T. maritima) Bound to tRNAPhe	Closeup of Catalytic Site, Residues 49-52 (3qir)

• The RNA is the catalytic component; this is a ribozyme

• Protein helps maintain RNA conformation, bind substrate, and aids in release of product

RNase D, which clips the 3'-end is all protein:

RNase D from E. coli (1yt3)	The Catalytic Site: Asp28, Asp85, Asp155

Now we need to add the CCA that terminates the 3'-end of all tRNAs. The enzyme operates as a dimer, with each chain working on an RNA:

tRNA Nucleotidyl Transferase (1sz1)

The nucleotides are added one by one in a single catalytic center in each protein, contrary to your text:

There is no template, except the enzyme.