Fig. 3. Crosslinker-based affinity purification of APP-interacting proteins from tecta. AP probes were crosslinked to surface-biotinylated tecta, then immunoprecipitated from lysates to identify associated proteins. Crosslinker was cleaved before gel analysis. (A) Western blot using NeutrAvidin-HRP to detect surface-biotinylated co-precipitated proteins. Asterisks mark the two predominant bands. (B-G) 2D gels for large-scale co-precipitation. Western blots for biotinylated proteins (B,E) were compared with silver-stained gels (C,D,F,G). Arrows indicate the predominant biotinylated proteins in B and corresponding locations in the silver-stained gels. This region was excised from gels in C and D for tandem mass spectrometry. Arrowhead indicates an additional spot specific for the AP-APPs co-IP: mass spectrometry identified several proteins, but these lacked obvious signal peptide or transmembrane domains and were not characterized further.