Laboratory of Structural Biology, Tsinghua University, Beijing, China.
FASEB J. 2010 Jan;24(1):242-52. doi: 10.1096/fj.09-140194. Epub 2009 Sep 25.
Phosphagen kinase (PK) family members catalyze the reversible phosphoryl transfer between phosphagen and ADP to reserve or release energy in cell energy metabolism. The structures of classic quaternary complexes of dimeric creatine kinase (CK) revealed asymmetric ligand binding states of two protomers, but the significance and mechanism remain unclear. To understand this negative cooperativity further, we determined the first structure of dimeric arginine kinase (dAK), another PK family member, at 1.75 A, as well as the structure of its ternary complex with AMPPNP and arginine. Further structural analysis shows that the ligand-free protomer in a ligand-bound dimer opens more widely than the protomers in a ligand-free dimer, which leads to three different states of a dAK protomer. The unexpected allostery of the ligand-free protomer in a ligand-bound dimer should be relayed from the ligand-binding-induced allostery of its adjacent protomer. Mutations that weaken the interprotomer connections dramatically reduced the catalytic activities of dAK, indicating the importance of the allosteric propagation mediated by the homodimer interface. These results suggest a reciprocating mechanism of dimeric PK, which is shared by other ATP related oligomeric enzymes, e.g., ATP synthase.
磷酸原激酶（PK）家族成员催化磷酸原和 ADP 之间的可逆磷酸转移，以在细胞能量代谢中储备或释放能量。二聚肌酸激酶（CK）的经典四元复合物的结构揭示了两个亚基的不对称配体结合状态，但意义和机制尚不清楚。为了进一步了解这种负协同作用，我们确定了另一种 PK 家族成员精氨酸激酶（dAK）的二聚体结构，在 1.75Å 的分辨率下，以及与 AMPPNP 和精氨酸形成的三元复合物的结构。进一步的结构分析表明，配体结合二聚体中无配体的亚基比无配体二聚体中的亚基打开得更宽，这导致了 dAK 亚基的三种不同状态。配体结合二聚体中无配体亚基的意外变构作用应该从其相邻亚基的配体结合诱导的变构作用中传递。削弱亚基间连接的突变显著降低了 dAK 的催化活性，表明由同源二聚体界面介导的变构传递的重要性。这些结果表明了二聚 PK 的一种往复机制，这种机制在其他与 ATP 相关的寡聚酶中是共享的，例如 ATP 合酶。
