Solving a Mason-Pfizer monkey virus (M-PMV) protein helped establish Foldit as a serious science tool.
The protein in question, a retroviral protease, had been known for 15 years. It had been solved by NMR (nuclear magnetic resonance) in 2003, but the NMR results were inconsistent with results from X-ray crystallography.
Puzzle 390 launched 17 December 2010, and completed 7 January 2011. Using 10 starting models taken from NMR results, Foldit players were able to determine the correct native structure of the protein.
The Foldit Contenders group was listed as one of the authors of the paper "Crystal structure of a monomeric retroviral protease solved by protein folding game players", published in Nature Structural & Molecular Biology in 2011. See the complete paper.
The results are also referenced in a couple of Foldit blog posts: Recent Exciting Discoveries by Foldit and Nature Structural & Molecular Biology paper online!.
This protein was also revisited in Puzzle 712, but for some reason, no images were captured for the wiki.