Swinger Kerren K, Lemberg Kathryn M, Zhang Ying, Rice Phoebe A
Department of Biochemistry and Molecular Biology, The University of Chicago, 920 East 58th Street, Chicago, IL 60637, USA.
EMBO J. 2003 Jul 15;22(14):3749-60. doi: 10.1093/emboj/cdg351.
HU and IHF are members of a family of prokaryotic proteins that interact with the DNA minor groove in a sequence-specific (IHF) or non-specific (HU) manner to induce and/or stabilize DNA bending. HU plays architectural roles in replication initiation, transcription regulation and site-specific recombination, and is associated with bacterial nucleoids. Cocrystal structures of Anabaena HU bound to DNA (1P71, 1P78, 1P51) reveal that while underlying proline intercalation and asymmetric charge neutralization mechanisms of DNA bending are similar for IHF and HU, HU stabilizes different DNA bend angles ( approximately 105-140 degrees ). The two bend angles within a single HU complex are not coplanar, and the resulting dihedral angle is consistent with negative supercoiling. Comparison of HU-DNA and IHF-DNA structures suggests that sharper bending is correlated with longer DNA binding sites and smaller dihedral angles. An HU-induced bend may be better modeled as a hinge, not a rigid bend. The ability to induce or stabilize varying bend angles is consistent with HU's role as an architectural cofactor in many different systems that may require differing geometries.
HU和IHF是原核生物蛋白质家族的成员，它们以序列特异性（IHF）或非特异性（HU）的方式与DNA小沟相互作用，以诱导和/或稳定DNA弯曲。HU在复制起始、转录调控和位点特异性重组中发挥结构作用，并与细菌类核相关。鱼腥藻HU与DNA结合的共晶体结构（1P71、1P78、1P51）表明，虽然IHF和HU在DNA弯曲的潜在脯氨酸嵌入和不对称电荷中和机制方面相似，但HU稳定不同的DNA弯曲角度（约105-140度）。单个HU复合物中的两个弯曲角度不共面，由此产生的二面角与负超螺旋一致。HU-DNA和IHF-DNA结构的比较表明，更尖锐的弯曲与更长的DNA结合位点和更小的二面角相关。HU诱导的弯曲可能更好地模拟为铰链，而不是刚性弯曲。诱导或稳定不同弯曲角度的能力与HU作为许多可能需要不同几何形状的不同系统中的结构辅助因子的作用一致。
