Recombinant Human ID3 (1-88) Fragment - A high-purity recombinant protein fragment encompassing the complete bHLH domain of DNA-binding protein inhibitor ID-3. This fragment serves as an essential tool for studying the molecular mechanisms of transcriptional regulation, cellular differentiation, and circadian rhythm control without the confounding effects of the full-length protein.

DNA-binding protein inhibitor ID-3 (Inhibitor of Differentiation 3) is a key transcriptional regulator that functions as a dominant-negative inhibitor of basic helix-loop-helix (bHLH) transcription factors. By forming heterodimers with bHLH proteins, ID3 prevents their DNA binding and transcriptional activity, thereby influencing critical cellular processes including growth, differentiation, apoptosis, angiogenesis, and neoplastic transformation. The protein plays a significant role in myogenesis by inhibiting skeletal muscle and cardiac myocyte differentiation while promoting muscle precursor cell proliferation. Additionally, ID3 regulates the circadian clock by repressing the transcriptional activity of the CLOCK-BMAL1 heterodimer. As a nuclear protein, ID3 exerts its regulatory functions within the nucleus, making it a central player in developmental and cellular regulatory pathways.