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首页> 外文期刊>The FEBS journal >Crystal structures of the regulatory subunit of Thr-sensitive aspartate kinase from Thermus thermophilus
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Crystal structures of the regulatory subunit of Thr-sensitive aspartate kinase from Thermus thermophilus

机译：嗜热栖热菌Thr敏感天冬氨酸激酶调节亚基的晶体结构

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摘要

Crystal structures of the regulatory subunit of Thr-sensitive aspartate kinase (AK; EC 2.7.2.4) from Thermus thermophilus (TtAKbeta) were determined at 2.15 A in the Thr-bound form (TtAKbeta-Thr) and at 2.98 A in the Thr-free form (TtAKbeta-free). Although both forms are crystallized as dimers, the contact surface area of the dimer interface in TtAKbeta-free (3200 A(2)) is smaller than that of TtAKbeta-Thr (3890 A(2)). Sedimentation equilibrium analyzed by ultracentrifugation revealed that TtAKbeta is present in equilibrium between a monomer and dimer, and that Thr binding shifts the equilibrium to dimer formation. In the absence of Thr, an outward shift of beta-strands near the Thr-binding site (site 1) and a concomitant loss of the electron density of the loop region between beta3 and beta4 near the Thr-binding site are observed. The mechanism of regulation by Thr is discussed on the basis of the crystal structures. TtAKbeta has higher thermostability than the regulatory subunit of Corynebacterium glutamicum AK, with a difference in denaturation temperature (T(m)) of 40 degrees C. Comparison of the crystal structures of TtAKbeta and the regulatory subunit of C. glutamicum AK showed that the well-packed hydrophobic core and high Pro content in loops contribute to the high thermostability of TtAKbeta.
机译：嗜热栖热菌（TtAKbeta）的Thr敏感天门冬氨酸激酶（AK; EC 2.7.2.4）调节亚基的晶体结构在Thr结合形式（TtAKbeta-Thr）为2.15 A时在Thr-中为2.98 A确定。自由形式（不含TtAKbeta）。尽管两种形式都结晶为二聚体，但无TtAKbeta（3200 A（2））中二聚体界面的接触表面积小于TtAKbeta-Thr（3890 A（2））。通过超速离心分析的沉降平衡表明，TtAKbeta存在于单体与二聚体之间的平衡中，Thr结合将平衡转移至二聚体的形成。在不存在Thr的情况下，观察到Thr结合位点附近的β链向外移动（位点1），并且在Thr结合位点附近的β3和β4之间的环区域的电子密度随之损失。基于晶体结构讨论了通过Thr调节的机理。 TtAKbeta具有比谷氨酸棒杆菌AK的调节亚基更高的热稳定性，变性温度（T（m））相差40摄氏度。TtAKbeta和谷氨酸棒杆菌AK的调节亚基的晶体结构比较表明，堆积的疏水核和环中高Pro含量有助于TtAKbeta的高热稳定性。

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