Tokunaga Hiroko, Arakawa Tsutomu, Tokunaga Masao
Applied and Molecular Microbiology, Faculty of Agriculture, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan.
Alliance Protein Laboratories, 6042 Cornerstone Court West, Suite A, San Diego, CA 92121, USA.
Int J Biol Macromol. 2014 May;66:66-73. doi: 10.1016/j.ijbiomac.2014.02.016. Epub 2014 Feb 16.
Nucleoside diphosphate kinase from a moderate halophile Halomonas sp. 593 (HaNDK) is dimer, while NDK from different origins has been shown to assemble into hexamer, or tetramer. Similar to HaNDK, halophilic NDK from Chromohalobacter salexigens DSM3043 (CsNDK) formed dimeric structure. Cysteine139 conserved between HaNDK and CsNDK is located in the monomer/monomer interface. Substitution of Cys139 for Ser caused dissociation of dimeric CsNDK into monomer in Tris buffer, as determined by field flow fractionation technique. Circular dichroism (CD) profile of the mutant CsNDK was nearly identical to the wild type CsNDK: however, the mutant CsNDK became more susceptible to "endproteinase GluC" cleavage, which could be suppressed by an NDK substrate, ATP. The monomer was enzymatically active, although it is possible that active structure is dimer in the presence of substrate.
中度嗜盐菌盐单胞菌属593（HaNDK）的核苷二磷酸激酶是二聚体，而来自不同来源的核苷二磷酸激酶已被证明可组装成六聚体或四聚体。与HaNDK相似，嗜盐嗜盐杆菌DSM3043（CsNDK）的嗜盐核苷二磷酸激酶形成二聚体结构。HaNDK和CsNDK之间保守的半胱氨酸139位于单体/单体界面。通过场流分级技术测定，在Tris缓冲液中，用丝氨酸取代半胱氨酸139会导致二聚体CsNDK解离为单体。突变型CsNDK的圆二色性（CD）图谱与野生型CsNDK几乎相同：然而，突变型CsNDK对“内蛋白酶GluC”的切割变得更敏感，但可被核苷二磷酸激酶底物ATP抑制。单体具有酶活性，尽管在有底物存在的情况下活性结构可能是二聚体。
