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=== Structural Architecture and DNA-Binding Mechanism===

The crystallographic structures of NolR reveal a homodimeric winged '''helix-turn-helix''' transcription factor, comprising two α-helical regions ('''α1 and α5''') forming the dimerization interface and a triangular configuration of helices ('''α2–α4''') that positions the conserved helix-turn-helix motif ('''α3–α4''') for DNA major groove binding. Notably, a distinctive "wing" composed of antiparallel β-sheets extends into the DNA minor groove. This architectural arrangement enables NolR to recognize '''asymmetric operator sequences'''—a remarkable feature that confers specificity and versatility in binding diverse target genes.

===The Gln56 Conformational Switch: A Novel Regulatory Innovation===

Perhaps the most striking discovery of this work is the identification of a **conformational switching mechanism** centered on **glutamine residue 56 (Gln56)**. This glutamine adopts different conformational states depending on the nucleotide composition of target DNA sequences. In the first half-site of the operator, Gln56 orients toward the adenine base (A2), while in the second half-site, its side-chain can flip away from thymine (T7') or reorient toward adenine (A7') depending on the sequence variation.

</StructureSection>

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 === Structural Architecture and DNA-Binding Mechanism===
 The crystallographic structures of NolR reveal a homodimeric winged '''helix-turn-helix''' transcription factor, comprising two α-helical regions ('''α1 and α5''') forming the dimerization interface and a triangular configuration of helices ('''α2–α4''') that positions the conserved helix-turn-helix motif ('''α3–α4''') for DNA major groove binding. Notably, a distinctive "wing" composed of antiparallel β-sheets extends into the DNA minor groove. This architectural arrangement enables NolR to recognize '''asymmetric operator sequences'''—a remarkable feature that confers specificity and versatility in binding diverse target genes.
+===The Gln56 Conformational Switch: A Novel Regulatory Innovation===
+Perhaps the most striking discovery of this work is the identification of a **conformational switching mechanism** centered on **glutamine residue 56 (Gln56)**. This glutamine adopts different conformational states depending on the nucleotide composition of target DNA sequences. In the first half-site of the operator, Gln56 orients toward the adenine base (A2), while in the second half-site, its side-chain can flip away from thymine (T7') or reorient toward adenine (A7') depending on the sequence variation.
 </StructureSection>