In enzymology, a polynucleotide adenylyltransferase is an enzyme

Enzyme

Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

 that catalyzes

Catalysis

Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....

 the chemical reaction

Chemical reaction

A chemical reaction is a process that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, such as heat, light or electricity...

ATP + RNAn diphosphate + RNAn⁺1

Thus, the two substrates

Substrate (biochemistry)

In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalyze chemical reactions involving the substrate. In the case of a single substrate, the substrate binds with the enzyme active site, and an enzyme-substrate complex is formed. The substrate is transformed into one or...

 of this enzyme are ATP

Adenosine triphosphate

Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...

 and RNA

RNA

Ribonucleic acid , or RNA, is one of the three major macromolecules that are essential for all known forms of life....

, whereas its two products

Product (chemistry)

Product are formed during chemical reactions as reagents are consumed. Products have lower energy than the reagents and are produced during the reaction according to the second law of thermodynamics. The released energy comes from changes in chemical bonds between atoms in reagent molecules and...

 are diphosphate and RNA with an extra adenosine nucleotide at its 3' end.

Naming

This enzyme belongs to the family of transferase

Transferase

In biochemistry, a transferase is an enzyme that catalyzes the transfer of a functional group from one molecule to another . For example, an enzyme that catalyzed this reaction would be a transferase:In this example, A would be the donor, and B would be the acceptor...

s, specifically those transferring phosphorus-containing nucleotide

Nucleotide

Nucleotides are molecules that, when joined together, make up the structural units of RNA and DNA. In addition, nucleotides participate in cellular signaling , and are incorporated into important cofactors of enzymatic reactions...

 groups (nucleotidyltransferase

Nucleotidyltransferase

Nucleotidyltransferases are transferase enzymes of phosphorus-containing groups, e.g., substituents of nucleotidylic acids or simply nucleoside monophosphates...

s). The systematic name of this enzyme class is ATP:polynucleotide adenylyltransferase.

Other names in common use include:

• NTP polymerase
• RNA adenylating enzyme
• AMP polynucleotidylexotransferase
• ATP-polynucleotide adenylyltransferase
• ATP:polynucleotidylexotransferase
• Poly(A) polymerase
• Poly(A) synthetase
• Polyadenylate nucleotidyltransferase
• Polyadenylate polymerase
• Polyadenylate synthetase
• Polyadenylic acid polymerase
• Polyadenylic polymerase
• Terminal riboadenylate transferase
• Poly(A) hydrolase
• RNA formation factors
• PF1
• Adenosine triphosphate:ribonucleic acid adenylyltransferase

Function

This enzyme is responsible for the addition of the 3' polyadenine tail

Polyadenylation

Polyadenylation is the addition of a poly tail to an RNA molecule. The poly tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases. In eukaryotes, polyadenylation is part of the process that produces mature messenger RNA for translation...

 to a newly synthesized pre-messenger RNA

Messenger RNA

Messenger RNA is a molecule of RNA encoding a chemical "blueprint" for a protein product. mRNA is transcribed from a DNA template, and carries coding information to the sites of protein synthesis: the ribosomes. Here, the nucleic acid polymer is translated into a polymer of amino acids: a protein...

 (pre-mRNA) molecule during the process of gene transcription

Transcription (genetics)

Transcription is the process of creating a complementary RNA copy of a sequence of DNA. Both RNA and DNA are nucleic acids, which use base pairs of nucleotides as a complementary language that can be converted back and forth from DNA to RNA by the action of the correct enzymes...

. The protein is the final addition to a large protein complex

Protein complex

A multiprotein complex is a group of two or more associated polypeptide chains. If the different polypeptide chains contain different protein domain, the resulting multiprotein complex can have multiple catalytic functions...

 that also contains smaller assemblies known as the cleavage and polyadenylation specificity factor

Cleavage and polyadenylation specificity factor

Cleavage and polyadenylation specificity factor is involved in the cleavage of the 3' signaling region from a newly synthesized pre-messenger RNA molecule in the process of gene transcription...

 (CPSF) and cleavage stimulatory factor

Cleavage stimulatory factor

Cleavage stimulatory factor or cleavage stimulation factor is a heterotrimeric protein of about 200 kilodaltons that is involved in the cleavage of the 3' signaling region from a newly synthesized pre-messenger RNA molecule...

 (CtSF) and its binding is a necessary prerequisite to the cleavage of the 3' end of the pre-mRNA. After cleavage of the 3' signaling region that directs the assembly of the complex, PAP adds the polyadenine tail to the new 3' end.

The rate at which PAP adds adenine

Adenine

Adenine is a nucleobase with a variety of roles in biochemistry including cellular respiration, in the form of both the energy-rich adenosine triphosphate and the cofactors nicotinamide adenine dinucleotide and flavin adenine dinucleotide , and protein synthesis, as a chemical component of DNA...

 nucleotide

Nucleotide

Nucleotides are molecules that, when joined together, make up the structural units of RNA and DNA. In addition, nucleotides participate in cellular signaling , and are incorporated into important cofactors of enzymatic reactions...

s is dependent on the presence of another regulatory protein, PABPII

PABPII

PABPII, or polyadenine binding protein II, is a protein involved in the assembly of the polyadenine tail added to newly synthesized pre-messenger RNA molecules during the process of gene transcription. It is a regulatory protein that controls the rate at which polyadenine polymerase adds adenine...

 (poly-adenine binding protein II). The first few nucleotides added by PAP are added very slowly, but the short polyadenine tail is then bound by PABPII, which accelerates the rate of adenine addition by PAP. The final tail is about 200-250 adenine nucleotides long.

PAP is phosphorylated

Phosphorylation

Phosphorylation is the addition of a phosphate group to a protein or other organic molecule. Phosphorylation activates or deactivates many protein enzymes....

 by , a key regulator of the cell cycle

Cell cycle

The cell cycle, or cell-division cycle, is the series of events that takes place in a cell leading to its division and duplication . In cells without a nucleus , the cell cycle occurs via a process termed binary fission...

. High phosphorylation levels decrease PAP activity.

Structural studies

As of late 2007, 27 structures

Tertiary structure

In biochemistry and molecular biology, the tertiary structure of a protein or any other macromolecule is its three-dimensional structure, as defined by the atomic coordinates.-Relationship to primary structure:...

 have been solved for this class of enzymes, with PDB

Protein Data Bank

The Protein Data Bank is a repository for the 3-D structural data of large biological molecules, such as proteins and nucleic acids....

accession codes , , , , , , , , , , , , , , , , , , , , , , , , , , and .