Introducing Protein Intrinsic Disorder

Proteins are the major component of the living cell. They play crucial roles in the maintenance of life, and their dysfunctions are known to cause different pathologies. Simple amino acid propensities reflect some basic physical or sequence features. Such propensity-based predictors rely on simple statistics of amino acid propensity, on the physical/chemical features of amino acids, or on a preliminary concept on the physical background of disorder. Regions of missing electron density in the PDB are generally short, as long regions prevent crystallization. As such, short disorder is overrepresented in the database of disordered regions, and hence these predictors tend to perform better in predicting short disorder than long disorder. Predictors can also be classified based on the binary nature of the prediction. Examples of binary predictors are the CH plot and the cumulative distribution function (CDF) analysis.