Schlichting I, Reinstein J
Max-Planck-Institut für molekulare Physiologie, Abteilung physikalische Biochemie, Rheinlanddamm 201, D-44139 Dortmund, Germany.
Biochemistry. 1997 Aug 5;36(31):9290-6. doi: 10.1021/bi970974c.
UMP/CMP kinase from Dictyostelium discoideum (UmpKdicty) catalyzes the specific transfer of the terminal phosphate of ATP to UMP or CMP. Crystal structures of UmpKdicty with substrates and the transition state analogs AlF3 or BeF2 that lock UmpKdicty in active conformations were solved. The positions of the catalytic Mg2+ and the highly conserved lysine of the P loop are virtually invariant in the different structures. In contrast, catalytic arginines move to stabilize charges that develop during this reaction. The location of the arginines indicates formation of negative charges during the reaction at the transferred phosphoryl group, but not at the phosphate bridging oxygen atoms. This is consistent with an associative phosphoryl transfer mechanism but not with a dissociative one.
盘基网柄菌的尿苷一磷酸/胞苷一磷酸激酶（UmpKdicty）催化将ATP的末端磷酸基团特异性转移至UMP或CMP。解析了UmpKdicty与底物以及将UmpKdicty锁定在活性构象的过渡态类似物AlF3或BeF2的晶体结构。在不同结构中，催化性Mg2+和P环中高度保守的赖氨酸的位置几乎不变。相比之下，催化性精氨酸会移动以稳定反应过程中产生的电荷。精氨酸的位置表明，反应过程中在转移的磷酰基上形成了负电荷，但在磷酸桥连氧原子上没有形成负电荷。这与缔合性磷酰基转移机制一致，而与解离性机制不一致。
