Evidence for common sites of contact between the antisigma factor SpoIIAB and its partners SpoIIAA and the developmental transcription factor sigmaF in Bacillus subtilis.
Evidence for common sites of contact between the antisigma factor SpoIIAB and its partners SpoIIAA and the developmental transcription factor sigmaF in Bacillus subtilis.
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DOI：
10.1006/jmbi.1998.2201
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发表时间：
1998-12
影响因子：
5.6
通讯作者：
D. Garsin;D. M. Paskowitz;L. Duncan;Richard Losick
中科院分区：
文献类型：
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作者：
D. Garsin;D. M. Paskowitz;L. Duncan;Richard Losick
枯草芽孢杆菌中发育转录因子 sigmaF 的活性由涉及双功能蛋白 SpoIIAB 的开关控制。 SpoIIAB 是一种抗 sigma 因子，可与 sigmaF 和替代伙伴蛋白 SpoIIAA 形成复合物。 SpoIIAB 也是一种蛋白激酶，可通过在丝氨酸残基上磷酸化 SpoIIAA 使其失活。我们试图通过筛选 sigmaF 激活缺陷的突变体来鉴定 SpoIIAB 中参与 SpoIIAB-SpoIIAA 复合物形成的氨基酸。这种遗传筛选与生化分析和侧链缺失（丙氨酸取代）突变体的构建相结合，鉴定出了 SpoIIAB N 端区域中可以接触 SpoIIAA 的氨基酸侧链。出乎意料的是，与 sigmaF 的结合需要与 SpoIIAA 接触的相同氨基酸侧链（R20 和 N50），并且可能代表与 sigmaF 的接触位点。我们认为 SpoIIAB 的 N 端区域形成一个结合表面，负责形成 SpoIIAB-SpoIIAA 和 SpoIIAB-sigmaF 复合物，并且在某些情况下，相同的氨基酸侧链接触两种伙伴蛋白。 N50 也是被称为 N-box 的氨基酸序列同源区域的定义残基，该区域由 SpoIIAB 和相关丝氨酸蛋白激酶以及在组氨酸残基处进行自磷酸化的机制不同的蛋白激酶家族的成员共享。我们讨论了这一发现对组氨酸自磷酸化机制的影响。
The activity of the developmental transcription factor sigmaF in Bacillus subtilis is governed by a switch involving the dual function protein SpoIIAB. SpoIIAB is an antisigma factor that forms complexes with sigmaF and with an alternative partner protein SpoIIAA. SpoIIAB is also a protein kinase that can inactivate SpoIIAA by phosphorylating it on a serine residue. We sought to identify amino acids in SpoIIAB that are involved in the formation of the SpoIIAB-SpoIIAA complex by screening for mutants that were defective in the activation of sigmaF. This genetic screen, in combination with biochemical analysis and the construction of loss-of-side-chain (alanine substitution) mutants, led to the identification of amino acid side-chains in the N-terminal region of SpoIIAB that could contact SpoIIAA. Unexpectedly, the same amino acid side-chains (R20 and N50) that appear to touch SpoIIAA are required for binding to, and may represent sites of contact with, sigmaF. We propose that the N-terminal region of SpoIIAB forms a binding surface that is responsible for the formation of both the SpoIIAB-SpoIIAA and the SpoIIAB-sigmaF complexes, and that in some cases the same amino acid side-chains contact both partner proteins. N50 is also the defining residue of a region of amino acid sequence homology known as the N-box that is shared by SpoIIAB and related serine protein kinases, as well as by members of a mechanistically dissimilar family of protein kinases that undergo autophosphorylation at a histidine residue. We discuss the implications of this finding for the mechanism of histidine autophosphorylation.