Proteins: A Mosaic Pattern to Rule Them All?

A specific pattern can be found in protein 3D structures when considering the position and chemical type of amino acids. This pattern, described by the Mosaic Q model, is quantified by a descriptor 'Q' which depends almost exclusively on the protein's size (number of amino acids) rather than its shape or origin. This finding is based on the analysis of over 160,000 X-Ray-determined protein structures from the RCSB PDB database. Stochastic simulations were used to validate the model, demonstrating that the observed empirical curve is non-trivial and corresponds to a specific arrangement of amino acid clusters. The model provides a quantitative framework for a potentially fundamental organizational principle in proteins.