Protein complexes: structure prediction challenges for the 21st century.

Only a tiny fraction of the many hundreds of known protein complexes are also of known three-dimensional structure. The experimental difficulties surrounding structure determination of complexes make methods that are able to predict structures paramount. The challenge of predicting complex structures is daunting and raises many issues that need to be addressed. To produce the best models, new prediction methods have to somehow combine partial structures with a mixed bag of experimental data, including interactions and low-resolution electron microscopy images.