Analysis of an enzymatic domain that is involved in specificity of phosphoryl donors, polyphosphate and ATP

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Inorganic polyphosphate (polyP) is a linear polymer of phosphate linked by high energy phosphoanhydride bonds. PolyP is found in abundance in volcanic condensates. Therefore, some investigators consider that polyP may be energy currency for prebiotic life. We found that a strictly polyP-dependent glucokinase in Microlunatus phosphovorus. ATP is used to phosphorylate glucose in many organisms, while polyP is used in this microorganism. We determined a primary structure of this polyP-glucokinase, and found that the active site residues are conserved in both of ATP- and polyP-glucokinase. However, a domain IIB is only observed in ATP-glucokinase. We considered that ATP-glucokinase is evolved from polyP-glucokinase. In this study, we wanted to reveal structural changes in glucokinase when it acquire the domain IIB and changes its phosphoryl donor. First we purified polyP-glucokinase from E.coli recombinant. The purified enzyme is further concentrated and used in order to find crystalization condition. Finally we succeeded in crystalization of polyP-glucokinase and obtaining X-ray diffraction pattern with two-angstrom resolution. We have not yet solved, but succeeded in predicting its three-dimensional structure. We predicted that polyP-glucokinase acquired adenosine recognizing domain and evolved to ATP-glucokinase.