A protein folding degree measure and its dependence on crystal packing, protein size, secondary structure, and domain structural class.
Comparing two or more protein structures with respect to their degree of folding is common practice in structural biology despite the fact that there is no scale for a folding degree. Here we introduce a formal definition of a folding degree, capable of quantitative characterization. This enables ordering among protein chains based on their degree of folding. The folding degree of a data set of 152 representative nonhomologous proteins is then studied. We demonstrate that the variation in the folding degree seen for this data set is not due to crystallization artifacts or experimental conditions, such as resolution, refinement protocol, pH, or temperature. A good linear relationship is observed between the folding degree and the percentages of secondary structures in the protein. The folding degree is able to account for the small changes produced in the structure due to crystal packing and temperature. Automating the classification of proteins into their respective structural domain classes, namely mainly-alpha, mainly-beta, and alpha-beta, is also possible.
Estrada
Ernesto
E
Molecular Informatics, X-ray Unit, RIAIDT, Edificio CACTUS, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain. estrada66@yahoo.com
D019295:Computational Biology; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D008958:Models, Molecular; D008970:Molecular Weight; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary