The WT b or control N9K b peptide at 200 nM was then applied to PTHs in culture and near zero distance cross-linking was induced by UV irradiation. The cross-linked peptide and associated partners were precipitated by streptavidin T1 beads and separated by SDS-PAGE. Western blotting using 2D3 as a probe revealed several bands including a major smeared band with apparent molecular weight of ∼65 kDa in the WT b but not N9K b cross-linked sample. The 65-kDa band shifted to ∼43 kDa upon treatment with the deglycosylation enzyme PNGase F (Figure 2A, left) , indicating that it is highly N-glycosylated. The WT b cross-linked protein apparently contained no intermolecular disulfide bonds as it migrated similarly under both nonreducing and reducing conditions (Figure 2A, right) . The non-photoreactive Myr-47/WT peptide but not its N9K mutant peptide effectively competed with WT b for cross-linking to the 65-kDa band ( Figure 2B) . The cross-linked protein from PTHs decreased in abundance rapidly over time during culture ( Figure 2C) . We also examined primary human hepatocytes (PHHs) in the crosslinking experiments. Bands with slightly smaller molecular weights than those seen in the PTH cells were also observed in PHHs ( Figure 2D) .