Mammalian Poly(A) Polymerase
Bos taurus (bovine)
Messenger RNA molecules serve as crucial intermediates between genes and their encoded proteins. mRNAs are composed of chains of nucleotides, and most eukaryotic mRNA molecules contain a long tract of adenosine nucleotides at the 3' end. Following transcription, mRNA precursors (pre-mRNA) goes through a series of modifications, including capping at the 5' end, splicing and addition of a 3' poly(A) tail. In eukaryotes, polyadenylation of pre-mRNA plays an essential role in the initiation step of protein synthesis, as well as in the export from its site of production in the cell nucleus, translation into protein, and stability of mRNAs.Poly(A) polymerase (PAP) is a key enzyme of the polyadenylation of pre-mRNA, which specifically incorporates ATP at the 3' end of mRNA. PAPs belong to a large superfamily of nucleotidyl transferases.
The structure reported here shows a C-terminal truncation mutant of bovine PAP bound to an ATP analog. Like other nucleotidyl transferases, PAP is composed of three domains but the arrangement of them is quite different from other nucleic acid polymerases. This study provides a structural basis for ATP selection by poly(A) polymerase.
Protein Data Bank (PDB)
author: Aki Nagata