Crystallization of protein–protein complexes

Crystallizing protein–protein complexes remains a rate-limiting step in their structure characterization. Crystallization conditions for the known protein–protein complexes have been surveyed in both the Protein Data Bank and the BMCD database. Compared with non-complexed proteins, crystallization conditions for protein–protein complexes are less diverse and heavily favor (71% versus 27%) polyethylene glycols (PEG) rather than ammonium sulfate or other high-salt crystallization conditions. The results suggest that the stability of protein complexes limits their available crystallization configuration space. Based on the survey, a set of sparse-matrix screen conditions was designed.