Which motif does TBP use to bind DNA?

TBP, or TATA-binding protein, utilizes a specific structural motif to bind to DNA. The correct answer is the beta sheet motif. TBP contains a prominent configuration formed by a series of beta sheets that create a saddle-like shape. This structural conformation is critical because it allows TBP to interact effectively with the TATA box in the promoter region of genes.

The binding occurs through the insertion of the TBP into the DNA helix, where it bends the DNA significantly. This bending is necessary for the proper formation of the transcription pre-initiation complex. The rigid nature of the beta sheets provides the necessary stability and orientation for the protein to make specific interactions with the DNA, ensuring that transcription can be initiated correctly.

Other motifs, such as alpha helices or coiled-coils, do play important roles in various protein-DNA interactions but are not the primary structural feature utilized by TBP. Similarly, the zinc finger motif is more commonly associated with other types of DNA-binding proteins that recognize specific sequences through distinct structural configurations. Thus, understanding TBP's use of beta sheets to bind DNA highlights the complexity and specificity of protein-DNA interactions fundamental to the transcription process.