Protein Domain Architecture
The epidermal growth factor receptor (EGFR) exemplifies this, containing an extracellular ligand-binding domain, a transmembrane domain, and an intracellular kinase domain.
Proteins are linear chains of amino acids that fold into three-dimensional shapes, and rather than each having a unique monolithic structure, most proteins consist of multiple structural domains - compact regions of 40-400 amino acids that fold independently and perform discrete functions. The epidermal growth factor receptor (EGFR) exemplifies this, containing an extracellular ligand-binding domain, a transmembrane domain, and an intracellular kinase domain. This domain modularity enables combinatorial evolution: approximately 4,000 well-characterized domain families have been recombined in various ways to produce hundreds of thousands of distinct proteins. The same DNA-binding domain appears in hundreds of different transcription factors; the same kinase domain architecture appears in over 500 human protein kinases.
Business Application of Protein Domain Architecture
Protein domain architecture demonstrates how modular building blocks can be recombined to create diverse functional outcomes from a limited toolkit - analogous to how standardized business components can be assembled into varied product or service offerings.