About Guanylate kinase 1 / GUK1:
Guanylate kinase also referred to as GUK1 is an enzyme. It has two substrates, GMP and ATP and its products are GDP and ADP. This enzyme is part of the family of transferases and is specifically part of a group for transferring phosphorus-containing groups.
GUK1 Structure
Research has shown that Guanylate Kinase 1 has a similar structure to that of the protein A57R. Also known as SalG2R, this comes from certain strains of the Vaccina virus.
Similar to various NMP kinases, this enzyme consists of three particular domains that are dynamic. These are the LID, CORE and NMP-binding domains. Research has shown that there are small yet significant movements for the LID domain as well as larger more dramatic movements of the GMP-binding domain. This was found by comparing structures between the GK.GMP and apo-Gk.
Furthermore, the large movements do seem to involve a rotation that goes around a hinge axis which is effective. It is virtually parallel with helix 3 which connect to the CORE and GMP-binding domains. It also has particularly higher temperature factors as well. Thee helix 3 also plays a significant role in the movement of the domain. Since the structure for the recombinant GKGMP is superimposed of the native GK.GMP, it has been suggested that the N-terminal acetylation does not have a particularly significant impact on GKs three-dimensional structure.
Guanylate kinase 1 Function
The enzyme does participate in purine metabolism. This refers to the breakdown and synthesis of purines that are present and detectable in a wide range of different organisms.
Guanylate kinase does catalyze ATP-dependent phosphorylation into GDP from GMP. Its main function is to recycle GMP as well as more indirection cGMP. This occurs in low eukaryotes like a year, prokaryotes such as Escherichia coli as well as in vertebrates.
It is a monomeric protein that is highly conserved and made up of roughly 200 amino acids.
GUK1 Interactions
Various studies have highlighted and explored the chemical interactions between this enzyme. Specifically, one study explored the molecular interaction that occurred between pp(p)Gpp, as well as GMK. This revealed the importance of the interaction within adapting to starvation. In the interaction pp(p)Gpp bindings to the active site of GMP and totally inhibits the enzyme. This does prevent the conversion of GMP to GDP that we have previously discussed. Instead, it results in the accumulation of GMP as well as amino acid downshift. If the activation and interaction are abolished it then leads to amino acid starvation.
Guanylate kinase-1 Mechanism
The above study also explored the mechanism underlying this interaction. It explored the question of which molecular mechanism is responsible for the inhibition of GMK and how significant is it for cellular physiology. The results of the study suggested that the interaction of (p)ppGpp is just one of many regulatory mechanisms that are used to reduce GTP levels. An absence does seem to ensure that an excess level of (p)ppGppp is created which thusmaintains low levels of GTP. Further research is necessary to further understand the mechanisms of this particular enzyme.