Flow chart of the screening process used to identify P. horikoshii OT3 protein-protein interactions. In this flow chart the construction of BIND and ACT samples by PCR is omitted. We selected 980 predicted soluble proteins using the SOSUI program , and applied 960 of 980 clones for the first assay. The details are given in Materials and methods and Additional data file 1. ACT, VP16 transcriptional activation domain; Bind, Gal4 DNA-binding domain; ORF, open reading frame.