Department of Biological Chemistry, David Geffen School of Medicine, Molecular Biology Institute, University of California Los Angeles, Los Angeles, California, USA.
PLoS One. 2012;7(7):e39688. doi: 10.1371/journal.pone.0039688. Epub 2012 Jul 2.
Human DiGeorge Critical Region 8 (DGCR8) is an essential microRNA (miRNA) processing factor that is activated via direct interaction with Fe(III) heme. In order for DGCR8 to bind heme, it must dimerize using a dimerization domain embedded within its heme-binding domain (HBD). We previously reported a crystal structure of the dimerization domain from human DGCR8, which demonstrated how dimerization results in the formation of a surface important for association with heme. Here, in an attempt to crystallize the HBD, we search for DGCR8 homologues and show that DGCR8 from Patiria miniata (bat star) also binds heme. The extinction coefficients (ε) of DGCR8-heme complexes are determined; these values are useful for biochemical analyses and allow us to estimate the heme occupancy of DGCR8 proteins. Additionally, we present the crystal structure of the Xenopus laevis dimerization domain. The structure is very similar to that of human DGCR8. Our results indicate that dimerization and heme binding are evolutionarily conserved properties of DGCR8 homologues not only in vertebrates, but also in at least some invertebrates.
人 DiGeorge 关键区 8（DGCR8）是一种必需的 microRNA（miRNA）加工因子，通过与 Fe（III）血红素的直接相互作用而被激活。为了使 DGCR8 结合血红素，它必须使用嵌入其血红素结合域（HBD）中的二聚化结构域进行二聚化。我们之前报道了人源 DGCR8 二聚化结构域的晶体结构，该结构显示了二聚化如何导致与血红素结合的表面的形成。在这里，我们试图结晶 HBD，寻找 DGCR8 同源物，并表明来自 Patiria miniata（蝙蝠星）的 DGCR8 也结合血红素。测定了 DGCR8-血红素复合物的消光系数（ε）；这些值对于生化分析很有用，并允许我们估计 DGCR8 蛋白的血红素占有率。此外，我们还展示了非洲爪蟾的二聚化结构域的晶体结构。该结构与人类 DGCR8 非常相似。我们的结果表明，二聚化和血红素结合是 DGCR8 同源物的进化保守特性，不仅在脊椎动物中，而且在至少一些无脊椎动物中也是如此。
