dGTP: Structure, function & importance in biotechnology

dGTP is one of the four deoxyribonucleotide triphosphates (dNTPs) that form the building blocks of DNA. dGTP, dATP, dCTP, and dTTP are essential for DNA synthesis and replication, providing the necessary components from which DNA is built. dGTP consists of a 2`-deoxyribose sugar, a guanine base, and three connected phosphate groups.

What is dGTP?

dGTP is on of the four deoxyribonucleotide triphosphates (dNTPs) from which the DNA is sythesized during DNA replication or DNA repair. dGTP is incorporated into the growing DNA strand by the enzyme DNA polymerase, which forms a new phosphodiester bond between dGTP and the desoxyribose sugar at the strand end. The triphosphate group of dGTP, when cleaved during dGTP incorporation, provides the necessary energy for the formation of these bonds, ensuring the continuous incorporation of dGTP and the other three NTPs into the DNA strand.

dGTP structure & full form

dGTP is one of the four building blocks (dGTP, dATP, dCTP, and dTTP) from which DNA is enzymatically synthesized during replication and DNA repair. dGTP is a deoxyribonucleotide triphosphate (dNTP) molecule. dGTP, dATP, dCTP, and dTTP each consist of a deoxyribose sugar to which the corresponding DNA base (guanine in the case of dGTP) is attached. In addition, dGTP and the other NTPs have a triphosphate residue attached to the 5′ OH group of the sugar.

dGTP function

DNA synthesis & dGTPs role

During DNA replication and repair, dGTP is incorporated into the DNA strand by a DNA polymerase. This enzyme catalyzes the reaction of dGTP with the 3′ OH group at the end of the DNA strand. At this step, a pyrophosphate molecule is released from the dGTP and a new phosphodiester bond is formed between dGTP and DNA. The cleavage of the dGTP triphosphate group releasing the pyrophosphate molecule provides the energy necessary for the polymerase to successfully attach dGTP to the expanding DNA strand. Base pairing between dGTP and a cytosine base from the DNA template strand ensures that dGTP is incorporated at the correct position. The base pairing of dGTP and cytosine is mediated by three hydrogen bonds, where dGTP has two hydrogen bond donors and one hydrogen bond acceptor. In the rare cases where dGTP is incorrectly incorporated, DNA repair enzymes are available to replace the dGTP with the correct nucleobase.

Involvement of dGTP in Cellular processes

dGTP is part of the tightly regulated intracellular DNA precursor pool. Here, cellular dGTP availability peaks during the S phase of the cell cycle to allow for proper DNA synthesis. Abnormal dGTP levels can threaten genome stability, cause mutations, and lead to replication stress and even cell cycle arrest. The dGTP pool in mammalian cells is replenished by de novo dGTP synthesis. The rate-limiting step of de novo dGTP synthesis is the reduction of guanosine diphosphate by the enzyme ribonucleotide reductase (RNR). The resulting deoxyguanosine diphosphate is then phosphorylated to form dGTP. In addition, nucleoside salvage and nucleoside/nucleotide catabolism affect cellular dGTP levels. Thus, dGTP, along with the other three natural dNTPs, plays a critical role in DNA metabolism, genome stability, and cell cycle control.

Effects of dGTP dysfunctions

To ensure proper DNA replication and repair, a balanced cellular dGTP level is important. Both too high and too low dGTP levels affect genome stability. If dGTP levels are abnormally high, the risk of misincorporation of dGTP during DNA replication is high, leading to point mutations. In contrast, abnormally low levels of dGTP in the cellular dNTP pool lead to replication stress: Low levels of dGTP impair DNA polymerase activity, thereby stalling replication forks and triggering cell cycle arrest. Thus, long-term impairment of dGTP homeostasis promotes mutagenesis, increases the risk of cancer, and may contribute to degenerative diseases and premature aging.

Applications of dGTP in biotechnology

dGTP is one of the four dNTP building blocks for DNA synthesis. dGTP is therefore essential for PCR, qPCR, and DNA sequencing. In molecular cloning, dGTP is essential for proper DNA amplification and extention. In addition, dGTP is vital for enzymatic assays involving DNA polymerases or reverse transcriptases.

Significance of dGTP in pharmaceutical biotechnology

dGTP plays a critical role in gene therapy and drug development. dGTP is a natural substrate of DNA polymerases. dGTP can, therefore, be used as a scaffold to design drugs that can inhibit these polymerases. For example, dGTP -derived drugs block DNA synthesis in antiviral and anticancer therapies. In gene therapy, dGTP plays a critical role in the in vitro synthesis of therapeutic DNA constructs and of PCR-generated vectors.