6m3d
X-ray crystal structure of tandemly connected engrailed homeodomains (EHD) with R53A mutations and DNA complexX-ray crystal structure of tandemly connected engrailed homeodomains (EHD) with R53A mutations and DNA complex
Structural highlights
FunctionHMEN_DROME This protein specifies the body segmentation pattern. It is required for the development of the central nervous system. Transcriptional regulator that represses activated promoters. Wg signaling operates by inactivating the SGG repression of EN autoactivation. Publication Abstract from PubMedSmall DNA-binding proteins that target desired sequences have the potential to act as a scaffold for molecular tools such as genome editing. In this study, an engrailed homeodomain (EHD) was chosen and it was evaluated whether it could be used as a molecular module that can connect to itself to recognize a longer target sequence. It was previously shown that two EHDs connected by a linker (EHD(2)) recognize a target sequence twice as long as that recognized by a single EHD in cells only when Arg53 in each EHD in the tandem protein is mutated to alanine (EHD[R53A])(2). To investigate the recognition mechanism of (EHD[R53A])(2), the crystal structure of the (EHD[R53A])(2)-DNA complex was determined at 1.6 A resolution. The individual EHDs were found to adopt the typical homeodomain fold. Most importantly, the base-specific interactions in the major groove necessary for the affinity/specificity of wild-type EHD were preserved in (EHD[R53A])(2). Bacterial assays confirmed that the base-specific interactions are retained under cellular conditions. These observations indicate that the R53A mutation only causes a loss of the arginine-phosphate interaction at the protein-DNA interface, which reduces the DNA-binding affinity compared with the wild type. It is therefore concluded that (EHD[R53A])(2) precisely recognizes tandem target sites within cells, enabling the individual EHDs to concurrently bind to the target sites with modest binding affinity. This suggests that modulation of the binding activity of each EHD is vital to construct a protein array that can precisely recognize a sequence with multiple target sites. Structural basis for designing an array of engrailed homeodomains.,Sunami T, Hirano Y, Tamada T, Kono H Acta Crystallogr D Struct Biol. 2020 Sep 1;76(Pt 9):824-833. doi: , 10.1107/S2059798320009237. Epub 2020 Aug 17. PMID:32876058[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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