The Department of Human Biology, Faculty of Natural Science, University of Haifa, Haifa, 3498838, Israel.
The Department of Human Biology, Faculty of Natural Science, University of Haifa, Haifa, 3498838, Israel.
Biochem Biophys Res Commun. 2018 Sep 18;503(4):2736-2741. doi: 10.1016/j.bbrc.2018.08.033. Epub 2018 Aug 13.
Regulators of G-protein Signaling (RGS) proteins inactivate heterotrimeric G proteins, thereby setting the duration of active signaling. In particular, the RGS RZ subfamily, which consists of RGS17, RGS19, and RGS20, mediates numerous physiological functions and human pathologies - mostly by functioning as GTPase Activating Proteins (GAPs) towards the Gα subfamily. Yet, which RZ subfamily members mediate particular functions and how their GAP activity and specificity are governed at the amino acid level is not well understood. Here, we show that all RZ subfamily members have similar and relatively low GAP activity towards Gα. We characterized four RZ-specific structural motifs that mediate this low activity, and suggest they perturb optimal interactions with the Gα subunit. Indeed, inserting these RZ-specific motifs into the representative high-activity RGS16 impaired GAP activity in a non-additive manner. Our results provide residue-level insights into the specificity determinants of the RZ subfamily, and enable to study their interactions in signaling cascades by using redesigned mutants such as those presented in this work.
G 蛋白信号调节因子（RGS）蛋白可使异三聚体 G 蛋白失活，从而控制活性信号的持续时间。特别是由 RGS17、RGS19 和 RGS20 组成的 RGS RZ 亚家族通过作为 Gα 亚家族的 GTP 酶激活蛋白（GAP），介导多种生理功能和人类病理。然而，RZ 亚家族成员介导特定功能的方式以及其 GAP 活性和特异性如何在氨基酸水平上受到调控，目前还不是很清楚。在这里，我们表明所有 RZ 亚家族成员对 Gα 的 GAP 活性相似且相对较低。我们鉴定了四个介导这种低活性的 RZ 特异性结构基序，并提出它们可能会干扰与 Gα 亚基的最佳相互作用。事实上，将这些 RZ 特异性基序插入代表性的高活性 RGS16 中，会以非加性的方式损害 GAP 活性。我们的研究结果提供了 RZ 亚家族特异性决定因素的残基水平的见解，并能够通过使用如本文中所展示的重新设计的突变体来研究它们在信号级联中的相互作用。
