Transcription factors that belong to the PadR family play an essential role in the transcriptional regulation of diverse biological processes by recognizing their cognate palindromic DNA sequences. Bacillus cereus harbors a gene that encodes a PadR-like protein (bcPLP; BC1756). bcPLP has not been structurally characterized, and it remains unelucidated how bcPLP interacts with a specific DNA sequence to function as a transcription factor. To provide structural insights into DNA recognition by bcPLP, we performed a structural study and a DNA-binding analysis of bcPLP. The crystal structure of bcPLP was determined at 1.92 Å resolution. bcPLP consists of two domains, an N-terminal domain (NTD) and a C-terminal domain (CTD), and forms a homodimer mainly using the CTD. In the structure, bcPLP contains a highly positively charged elongated patch in the NTD that serves as a putative DNA-binding site. Indeed, an electrophoresis mobility shift assay and a fluorescence polarization assay showed that bcPLP specifically recognizes a palindromic DNA sequence upstream of the bcPLP-encoding region. Moreover, based on our mutagenesis and modeling studies, we demonstrate that bcPLP interacts with dsDNA primarily using the Y19, Y41, P64, and K66 residues in the NTD.
Keywords: Bacillus cereus; Crystal structure; DNA recognition; PadR family; PadR-like protein; Transcriptional regulator.
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