Fig 4. Functional analysis of top 150 enriched proteins recovered from cells expressing biotin ligase fusion proteins.

Streptavidin-purified proteins identified by mass spectrometry from cells expressing biotin ligase fused to the N terminus of Ocln (BL-Occludin, left), the C terminus of Ocln (Occludin-BL, middle) or the N terminus of Cldn4 (BL-Claudin 4, right). Functional classification revealed similar distribution for the two Ocln constructs, although individual proteins within the functional groups trafficking-, signaling-, cell adhesion etc. vary, or are more or less abundant (higher or lower average normalized-PSM/OPN). Functional groups of proteins recovered from cells expressing biotin ligase fused to the N terminus of Cldn4 shows similar functional distribution of enriched proteins as both of the Ocln fusion proteins, although there are slightly more trafficking proteins tagged by BL-Cldn4. Enriched = ≥3-fold increase compared to biotin ligase alone (as determined by the average normalized PSM/OPN).