Observation of Pyrococcus protein-protein interactions in vitro and the effect of heat pre-incubation on synthesized proteins. An in vitro pull-down assay was carried out after incubation of proteins at 37°C (non-heat) or 75°C (heat). The results with or without biotinylated driver proteins are shown as 'driver +' or 'driver -', respectively, and 10% of the 35S-labeled proteins in the assay were treated as 'input'. The three hetero-interaction pairs that were biotinylated and 35S-labeled are as follows: lane 1, PH1354 and PH1355; lane 2, PH0795 and PH0017; lane 3, PH0245 and PH1553. Arrows indicate bands of 35S-labeled proteins that were precipitated with biotinylated interacting partners.