Jos Jansen

6 135 Discussion and conclusion Figure 1 flow chart regarding reciprocality. Derived from Szklarczyk et al, Genome Biol, 2012 (4) Proteomics On proteome level several large scale projects were (and are) undertaken to map human protein-protein interactions (PPIs).(5-8) These maps can aid in recognition of potential new targets. All these projects share their data in easy- to-use online databases.(9) Yeast 2 hybrid PPI is the oldest technique to study PPIs and depends on proximity of a split transcription factor. Disadvantages are that the proteins must be able to enter the yeast nucleus and it provides an indirect readout. More recent techniques involve affinity purification with beads or agarose, washing, fractioning andmass spectrometry analysis. Advantages are high-throughput and scalability. Disadvantages are that temporal interactions easily get lost and that the sample can become contaminated resulting in false positive identification. Although these PPI databases give a hint, additional experiments will always be required. For example, the BioGrid network gives interactions for all V-ATPase assembly factors with an uncharacterized protein, KIAA2013. Exome sequencing data of CDG patients without a genetic diagnose was tested for variants in KIAA2013, but no pathogenic variants were identified.