Mass spectrometry analysis of proteins co-purifying with Cdc10, a component of the MBF transcriptional complex, was performed both in a wild-type and in a whi5∆ background. Cdc10 was tagged with YFP at its C-terminal end and expressed from its endogenous promoter at its chromosomal locus. Cdc10-YFP was immunoprecipitated from cells cultured in MM-N medium for 16 hours, and co-purifying proteins were analysed by mass spectrometry. An untagged wild-type strain was used as a control.