Ligandbindingsdomein

Ligandbindingsdomein is a protein domain specialized for recognizing and binding a specific ligand. In English, this feature is commonly called the ligand-binding domain (LBD). Ligandbindingsdomein binds ligands such as small molecules, nucleotides, metal ions, peptides, or other proteins. Binding usually triggers a functional response, including conformational changes, altered activity, or assembly of signaling complexes. LBDs occur in receptors, transcription factors, enzymes, and transporters, and may be standalone domains or integrated into larger proteins. They exhibit structural diversity but share a pocket or groove formed by conserved residues that interact with the ligand. Specificity derives from the geometry and chemical complementarity of the pocket, and binding affinity can be modulated by cofactors, pH, and allosteric effects.

Role and significance: Ligandbindingsdomein regulate various biological processes by translating ligand binding into functional outcomes, such as gene expression changes in nuclear receptors, signal transduction in membrane receptors, or regulation of enzymatic activity. Examples include the ligand-binding domains of nuclear receptors that respond to steroid hormones and extracellular or periplasmic binding domains in transport and signaling proteins.

Study and applications: Knowledge of ligandbindingsdomein informs drug design and protein engineering. Methods used to study them include X-ray crystallography, NMR, and cryo-electron microscopy, as well as biophysical binding assays (isothermal titration calorimetry, surface plasmon resonance), mutagenesis, and computational docking.