Schumacher Maria A, Pearson Robert F, Møller Thorleif, Valentin-Hansen Poul, Brennan Richard G
Department of Biochemistry and Molecular Biology, Oregon Health and Science University, Portland, OR 97201-3098, USA.
EMBO J. 2002 Jul 1;21(13):3546-56. doi: 10.1093/emboj/cdf322.
In prokaryotes, Hfq regulates translation by modulating the structure of numerous RNA molecules by binding preferentially to A/U-rich sequences. To elucidate the mechanisms of target recognition and translation regulation by Hfq, we determined the crystal structures of the Staphylococcus aureus Hfq and an Hfq-RNA complex to 1.55 and 2.71 A resolution, respectively. The structures reveal that Hfq possesses the Sm-fold previously observed only in eukaryotes and archaea. However, unlike these heptameric Sm proteins, Hfq forms a homo-hexameric ring. The Hfq-RNA structure reveals that the single-stranded hepta-oligoribonucleotide binds in a circular conformation around a central basic cleft, whereby Tyr42 residues from adjacent subunits stack with six of the bases, and Gln8, outside the Sm motif, provides key protein-base contacts. Such binding suggests a mechanism for Hfq function.
在原核生物中，Hfq 通过优先结合富含 A/U 的序列来调节众多 RNA 分子的结构，从而调控翻译过程。为了阐明 Hfq 识别靶标和调控翻译的机制，我们分别测定了金黄色葡萄球菌 Hfq 及其与 RNA 复合物的晶体结构，分辨率分别为 1.55 Å 和 2.71 Å。结构显示，Hfq 具有此前仅在真核生物和古细菌中观察到的 Sm 折叠。然而，与这些七聚体 Sm 蛋白不同，Hfq 形成同型六聚体环。Hfq-RNA 结构表明，单链七聚寡核糖核苷酸以环状构象围绕中央碱性裂隙结合，相邻亚基的 Tyr42 残基与六个碱基堆积，Sm 基序之外的 Gln8 提供关键的蛋白质-碱基接触。这种结合方式提示了 Hfq 的功能机制。
