MODELLER

MODELLER is a popular computer program used in producing homology models of protein tertiary structures as well as quaternary structures (rarer). It implements a technique inspired by nuclear magnetic resonance known as satisfaction of spatial restraints, by which a set of geometrical criteria are used to create a probability density function for the location of each atom in the protein. The method relies on an input sequence alignment between the target amino acid sequence to be modeled and a template protein whose structure has been solved.

The program also incorporates limited functionality for ab initio structure prediction of loop regions of proteins, which are often highly variable even among homologous proteins and therefore difficult to predict by homology modeling.

MODELLER was originally written and is currently maintained by Andrej Sali at the University of California, San Francisco. Although it is freely available for academic use, graphical user interfaces and commercial versions are distributed by Accelrys.