Adenylate kinase (ADK, EC number 2.7.4.3) is a phosphotransferase which catalyzes the interconversion of ADP to ATP+AMP. ADK is important in cellular energy homeostasis. Dinucleotides polyphosphates like diadenosine pentaphosphate
(AP5) inhibit ADK. The images at the left and at the right correspond to one representative ADK, i.e. the crystal structure of Adenylate kinase from Desulfovibrio gigas (3l0p).
Adenylate kinase is an essential catalyst for cellular growth and multiplication. ADK belongs to a family of enzymes essential to life, and is highly abundant inside the cell. It is involved in the reversible transfer of the terminal phosphate group from Mg2+ATP to Mg2+AMP with high energy turnover: Mg2+ATP + AMP↔Mg2+ADP + ADP.
Adenylate kinases (ADK) from Gram-negative bacteria are generally devoid of metal ions in their LID domain. However, , zinc, cobalt and iron, have been found in ADK from Gram-negative bacteria. Crystal structures of substrate-free ADK from Desulfovibrio gigas with three different metal ions: (2xb4); (3l0s) and (3l0p) bound in its LID domain have been determined by X-ray crystallography. to each other with the same LID domain topology, the only change being the presence of the different metal atoms.
The structures of Zn- , Co- and Fe-ADK contain the and , which also include the AMP binding region. The LID domain harbors the , which is responsible for metal binding in a tetrahedral fashion. In the absence of any substrate, the LID domain of all holo forms of ADK was present in a fully open conformational state. The Core domain is . This Core domain mainly consists of a that keep the integrity of the tertiary structure of the enzyme. A with conserved sequence; G-X-X-G-X-G-K is present in the N-terminal region. The structures presented herein further reinforce the notion that the metal ion is purely structural, contributing to the stability of the LID domain.[1]
