An important membrane polypeptide in peroxisomes, the peroxisomal membrane protein 70 (PMP 70) is generally considered to be a member of the half ATP-binding cassette (ABC) transporter superfamily of proteins. The proteins and enzymes in this superfamily all contain ATP-binding folds and are believed to frequently function in transport across membranes. More specifically, PMP 70 has been associated with the metabolic transport of long chain acyl-CoA across peroxisomal membranes. Also, research suggests that an increase in PMP 70 presence is not involved in the propagation of peroxisomes. However, many of the details regarding the in vivo activities of PMP 70 are still unknown, but many properties are being actively investigated. Studies have demonstrated, for instance, that the isolated protein both homodimerizes and heterodimerizes, but the functional significance of this characteristic has not been adequately established.

In a double immunofluorescence labeling experiment, a culture of MDCK cells illustrated above was treated with a cocktail of mouse anti-histones (pan) and rabbit anti-PMP 70 (peroxisomal membrane protein) primary antibodies. The target proteins were subsequently visualized with goat anti-mouse and anti-rabbit secondary antibodies conjugated to Texas Red and Alexa Fluor 488, respectively. The filamentous actin cytoskeletal network was counterstained with Alexa Fluor 350 conjugated to phalloidin. The nuclei were counterstained with the DNA-specific fluorophore DAPI. Images were recorded in grayscale with a QImaging Retiga Fast-EXi camera system coupled to an Olympus BX-51 microscope equipped with bandpass emission fluorescence filter optical blocks provided by Omega Optical. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles.