The Protein Model Portal was developed as a module of the Protein Structure Initiative Knowledgebase (PSI KB). The goal of the Models Module was to develop a portal that gave access to the various models that can be leveraged from PSI targets and other experimental protein structures. The Protein Structure Initiative has been successful in determining the structures of many unique proteins in a high throughput manner. Still, the number of known protein sequences is much larger than the number of experimentally solved protein structures. Homology (or comparative) modeling methods make use of experimental protein structures to build models for evolutionary related proteins. Experimental structural biology and homology modeling thereby complement each other in the exploration of the protein structure space.

Reference: Haas J., Roth S., Arnold, K., Kiefer, F., Schmidt T., Bordoli, L. and Schwede, T. (2013). The Protein Model Portal - a comprehensive resource for protein structure and model information. Database doi: 10.1093/database/bat031