Probing the relation between protein-protein interactions and DNA binding for a linker mutant of the bacterial nucleoid protein H-NS

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• 作者：Mara Giangrossi ; Kathelijne Wintraecken ; Roberto Spurio ; Renko de Vries
• 关键词：Protein&ndash ; protein interaction ; DNA-binding protein ; Transcription regulation
• 刊名：Biochimica et Biophysica Acta - Proteins and Proteomics
• 出版年：February, 2014
• 年：2014
• 卷：1844
• 期：2
• 页码：339-345
• 全文大小：1092 K

文摘

We have investigated the relationship between oligomerization in solution and DNA binding for the bacterial nucleoid protein H-NS. This was done by comparing oligomerization and DNA binding of H-NS with that of a H-NS D68V-D71V linker mutant. The double linker mutation D68V-D71V, that makes the linker significantly more hydrophobic, leads to a dramatically enhanced and strongly temperature-dependent H-NS oligomerization in solution, as detected by dynamic light scattering. The DNA binding affinity of H-NS D68V-D71V for the hns promoter region is lower and has stronger temperature dependence than that of H-NS. DNase I footprinting experiments show that at high concentrations, regions protected by H-NS D68V-D71V are larger and less defined than for H-NS. In vitro transcription assays show that the enhanced protection also leads to enhanced transcriptional repression. Whereas the lower affinity of the H-NS D68V-D71V for DNA could be caused by competition between oligomerization in solution and oligomerization on DNA, the larger size of protected regions clearly confirms the notion that cooperative binding of H-NS to DNA is related to protein-protein interactions. These results emphasize the relative contributions of protein-protein interactions and substrate-dependent oligomerization in the control of gene repression operated by H-NS.