Conclusion for haloacid dehalogenase-like hydrolase domain containing 2

Structure

Structural comparison of 2HO4 using DALI revealed several homologs including the NagD-like protein of Thermotoga maritima, the β-Phosphoglucomutase of Lactococcus lactis, the β-Phosphoglucomutase of Escherichia coli, and the L-2-Haloacid dehalogenase of Xanthobacter autotrophicus. All of these proteins belong to the HAD superfamily and share three highly-conserved sequence motifs characteristic of the superfamily.

Using the structure and sequence alignments of 2HO4, we uncovered the conserved residues of the three motifs as well as the the Mg2+ binding site of the protein (Fig 4). The Asp-13 and Thr-17 of 2HO4 make up motif I, and the Asp-204 and Asp-209 make up motif III. These three motifs and the Mg2+ ion define the active site where the phosphatase activity takes place. During a dephosphorylation reaction, motif II binds the phosphoryl group of the substrate, while Motif III coordinates the Mg2+ ion as well as the phosphoryl group. The 2 Asp residues in motif I attack the phosphoryl substrate with the help of the metal ion. As a result, the phosphate group is cleaved off and a phosphaspartate intermediate is formed. A water molecule activated by motif I then attacks the phosphoaspartate intermediate to liberate an inorganic phosphate and the free enzyme (Rangarajan et al, 2006).

The Mg2+ ion is essential for the phosphatase activity at the aspartyl side chain of the active site. Such Mg2+ binding sites on conserved Asp residues are characteristic of the P-type ATPase members of the HAD superfamily, whereas, L-2-haloacid dehalogenase do not require a Mg2+ ion for their activity. Moreover, the 2 Asp residues in motif III are common to all enzymes of the HAD superfamily, except for L-2-haloacid dehalogenase and epoxide hydrolase. This suggests that 2HO4 may be a P-type ATPase and is involved in ATP hydrolysis.

P-ATPases transport ions across ion pumps and presumably undergo conformational changes to enable ion transport (Wang et al, 2001).

Function

The protein is named after its function of molecular hydrolase activity. It involves acting as catalysis to breakdown various bonds such as Carbon-Oxygen, Carbon-Nitrogen, Carbon-Carbon and phosphoric anhydride bonds. The latter part “domain containing 2” in the name refers to it having 2 domains in expressing the protein allocated mainly in the immune system but also in the brain. The name of the protein is directly related to the function. There’s evidence this protein not only exist in human speciestherefore it is possible to study other species to examine it's function in future research. From the basis structure of Haloacid dehalogenase superfamily, we understand the importance of hydrolases contains enzymes, phosphate ion and metal ion in the functional process. But unfortunately, there is still low level academic research proving its function in different part of body system.

Evolution

The mouse version of the gene is the closest to the ancestrial gene as indicated by the BLAST search and subsequent phylogenetic tree. There are 4 versions of the gene found in mice, one is well studied and seems to be the closest to the ancestor gene, one is an isoform and 2 are yet unnamed and thus unstudied. However, the closeness of the match suggests that it is of similar function. The human version is most closely resembling the chimpanzee and orangutan versions which is expected as those are the 2 animals most closely resembling the human genome overall.

Overall

Based on the structure of the protein, it belongs to the HAD family as it consists of the three conserved motifs important for the catalytic activity of the HAD proteins. The main function is as a phosphatase although the specific function is still not well studied. It is known that it is a conserved gene and the brief examination showed that the mouse versions of this gene are the closest to the ancestral gene.