From Proteopedia

Description

Adenylate kinase, commonly known as ADK, is a phosphotransferase enzyme. It has two important roles in various organisms. First, ADK plays an important role in nucleotide metabolism and synthesis. It also has a role in cellular energetics and homeostasis by phosphotransfer networks. Adenylate kinase catalyzes the reaction that forms ADP. The reaction is ATP + AMP = 2 ADP. In this catalyzed reaction, ADK molecules bind to AMP molecules and increase its binding affinity for ATP over other phosphate groups. However, adenylate kinase is also found in other molecules such as bacteria and yeast. ADK plays similar roles in bacteria and yeast, in that it involves cellular metabolism and energy. The following images highlight the structure of Adenylate kinase from Yersinia pestis, commonly known as yeast.

Structure

ADK is a protein made up of 214 amino acids. The of adenylate kinase can be seen here in purple with the ligand in the middle of the protein. The contains 12 alpha helices (light blue) and 7 beta sheets (yellow). The hold the protein together and give it shape. The are located towards the center of the protein, away from water. These residues are responsible for the overall conformation of the protein because of their "water fearing" nature. The are located mainly on the surface or outside of the protein where they will have contact with water and other molecules. The hydrophilic residues that are inside the enzyme are necessary for the enzyme to open its active site and allow substrate in. The is located in the center of protein. The ligand has six that allow it to bind to ADK's target protein (catalytic residues shown in white within the green ligand). These catalytic residues are known as the active site. The catalytic residues consist of arginine, aspartic acid, and lysine. The because it is located in the center of the protein (ligand is orange and water is displayed by space filling model). It is important to be shielded from water so that nothing interferes with the active site of the protein. The waters that are found in the interior are a result of the hydrophobic residues that are also found there. The ligands and catalytic residues of adenylate kinase are highly conserved throughout various organisms. This conservation indicates their importance to the protein's enzymatic function.

References

http://www.pnas.org/content/102/2/303.full

http://www.uniprot.org/uniprot/O69172

http://www.biomedcentral.com/1471-2199/13/31/abstract