Final answer:
Proteins interact with DNA's major groove, recognizing specific sequences through the shape and chemical properties of nitrogenous bases. The major groove allows transcription factors to bind with high specificity, enabling gene expression regulation. Access is facilitated by chromatin structure alteration via specific enzymes.
Step-by-step explanation:
The proteins that interact with DNA's major groove recognize specific sequences by reading the shape and chemical properties of the nitrogenous bases exposed within the groove. The asymmetrical spacing of DNA's sugar-phosphate backbones creates larger major grooves and smaller minor grooves. In the major groove, there is enough space for proteins, such as transcription factors, to make contact with the bases and 'read' the genetic information without disrupting the double helix. This interaction is critical for processes like transcription and replication, where proteins must recognize specific DNA sequences to bind and perform their functions.
Transcription factors bind specific DNA sequences in the major groove where the DNA double helix presents a particular pattern of hydrogen-bond donors and acceptors, as well as hydrophobic and hydrophilic regions that are sequence-specific. These features allow proteins to bind with high specificity to particular DNA sequences, enabling the regulation of gene expression.
DNA is packaged in cells as chromatin, a protein-DNA complex where the DNA is wrapped around histone proteins. Despite this dense packaging, certain enzymes can alter the chromatin structure, thereby allowing transcription factors and other proteins to access specific DNA sequences within the major groove.