Bao Qiuye, Christ Nicole, Dröge Peter
School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, 637551, Singapore.
Gene. 2004 Dec 8;343(1):99-106. doi: 10.1016/j.gene.2004.08.030.
Integration host factor (IHF) is a heterodimeric, site-specific DNA-binding and DNA-bending protein from Escherichia coli. It is involved in high-precision DNA transactions where it serves as a key architectural component of specialized nucleoprotein structures (snups). We described recently a novel approach for protein engineering using a single polypeptide chain IHF, termed scIHF2, as a first example. ScIHF2 is made up of the alpha subunit of IHF which was inserted into the beta subunit at peptide bond Q39/G40 via two short linkers. The monomer behaves very similarly to the heterodimeric, parental IHF in biochemical and functional assays. Here, we describe an extension of this approach in which we shortened either one or both linkers by one amino acid, thereby generating three new variants termed scIHF1, 3, and 4. These variants exhibit distinct DNA-binding properties, different phenotypes in site-specific integrative and excisive recombination by phage lambda integrase in vitro, as well as in pSC101 replication assays in a DeltaIHF E. coli host. We also introduced a K45E substitution within the alpha domain of scIHF3 and based on electrophoretic mobility shift assays (EMSAs), argue that it significantly changes the DNA trajectory within the protein-DNA complex. Our results indicate that IHF's pleiotropic roles in DNA transactions inside E. coli require different types of high-precision DNA architectural activities. The scIHF variants described here will help to explore further how flexible these requirements are.
整合宿主因子(IHF)是一种来自大肠杆菌的异源二聚体、位点特异性DNA结合和DNA弯曲蛋白。它参与高精度的DNA事务,在其中作为特殊核蛋白结构(snups)的关键结构成分。我们最近描述了一种新的蛋白质工程方法,使用单链多肽IHF(称为scIHF2)作为首个实例。ScIHF2由IHF的α亚基组成,该亚基通过两个短接头在肽键Q39/G40处插入β亚基中。在生化和功能测定中,单体的行为与异源二聚体亲本IHF非常相似。在这里,我们描述了这种方法的扩展,其中我们将一个或两个接头各缩短一个氨基酸,从而产生三个新变体,称为scIHF1、3和4。这些变体表现出不同的DNA结合特性,在体外由噬菌体λ整合酶进行的位点特异性整合和切除重组中以及在ΔIHF大肠杆菌宿主中的pSC101复制测定中表现出不同的表型。我们还在scIHF3的α结构域内引入了K45E取代,并基于电泳迁移率变动分析(EMSA)认为它显著改变了蛋白质-DNA复合物内的DNA轨迹。我们的结果表明,IHF在大肠杆菌内DNA事务中的多效性作用需要不同类型的高精度DNA结构活动。这里描述的scIHF变体将有助于进一步探索这些要求的灵活性。