Practice question

South-Western blotting was devised to identify DNA-binding proteins and to investigate DNA-protein interactions at molecular level. In workflow, proteins are separated by SDS-PAGE, blotted to membrane, and carefully renatured to restore native conformation. Membrane is then incubated with labeled double-stranded DNA probes harboring consensus binding motifs of transcription factors. Specific retention of probe indicates protein possesses sequence-specific DNA-binding domain. By linking molecular weight information to binding activity, technique helps discover novel transcription factors, compare isoforms, and evaluate effects of mutations on DNA recognition without requiring prior chromatographic purification.