MEASURING COLOCALIZATION OF PROTEINS IN SUBCELLULAR STRUCTURES
In the simple schematic example shown to the right, a plasma membrane protein depicted in green is degraded in lysosomes (depicted in red) under certain conditions.
Colocalization is a quantitative measurement using pixel intensities of two (sometimes three) labels. In this example the degree of colocalization is measured between the protein depicted in green and the lysosomal marker depicted in red.
Perfect colocalization is rare but this approach can be used to assess the degree of association between pairs of proteins or markers.
Colocalization can also be constrained by a third marker. For example, analysis of two transcription factors constrained by the nuclear mask Hoechst.