Grasser Klaus D, Grill Simon, Duroux Meg, Launholt Dorte, Thomsen Malene S, Nielsen Birthe V, Nielsen Hanne K, Merkle Thomas
Institute of Life Sciences, Aalborg University, Sohngaardsholmsvej 49, DK-9000 Aalborg, Denmark.
Biochemistry. 2004 Feb 10;43(5):1309-14. doi: 10.1021/bi035931c.
The high-mobility group (HMG) proteins of the HMGB family are chromatin-associated proteins that act as architectural factors in various nucleoprotein structures, which regulate DNA-dependent processes such as transcription and recombination. Database analyses revealed that in addition to the previously identified HMGB1-HMGB5 proteins, the Arabidopsis genome encodes at least three other family members having the typical overall structure of a central HMG-box DNA binding domain, which is flanked by basic and acidic regions. These novel HMGB proteins display some structural differences, when compared to HMGB1-HMGB5. Therefore, a representative of the identified proteins, now termed HMGB6, was further analyzed. The HMGB6 protein of approximately 27 kDa is the largest plant HMGB protein identified so far. This is essentially due to its unusually extended N-terminal domain of 109 amino acid residues. Subcellular localization experiments demonstrate that it is a nuclear protein. According to CD measurements, HMGB6 has an alpha-helical HMG-box domain. HMGB6 can bind DNA structure-specifically, and it is a substrate for the protein kinase CK2alpha. Because of these features, HMGB6, and presumably its relatives, can be considered members of the plant HMGB protein family. Hence, eight different chromosomal HMGB proteins are expressed in Arabidopsis, and they may serve specialized architectural functions assisting various DNA-dependent processes.
高迁移率族（HMG）蛋白家族中的HMGB蛋白是与染色质相关的蛋白质，在各种核蛋白结构中作为结构因子发挥作用，调节诸如转录和重组等依赖DNA的过程。数据库分析表明，除了先前鉴定出的HMGB1-HMGB5蛋白外，拟南芥基因组还编码至少另外三个家族成员，它们具有典型的中央HMG-box DNA结合结构域的整体结构，该结构域两侧是碱性和酸性区域。与HMGB1-HMGB5相比，这些新的HMGB蛋白显示出一些结构差异。因此，对鉴定出的一种蛋白质（现称为HMGB6）进行了进一步分析。大约27 kDa的HMGB6蛋白是迄今为止鉴定出的最大的植物HMGB蛋白。这主要是由于其109个氨基酸残基的异常延伸的N端结构域。亚细胞定位实验表明它是一种核蛋白。根据圆二色性测量，HMGB6具有α-螺旋HMG-box结构域。HMGB6可以特异性结合DNA结构，并且它是蛋白激酶CK2α的底物。由于这些特性，HMGB6及其可能的相关蛋白可被视为植物HMGB蛋白家族的成员。因此，拟南芥中表达了八种不同的染色体HMGB蛋白，它们可能发挥特殊的结构功能，协助各种依赖DNA的过程。
