Fig. 2. Immunoprecipitation of brain TPG and identification of the PGs1 subunit. (A) Silver staining of Fraction IV (lane 1) and the IP fraction obtained with mAb206 (lane 2). In addition to the light (LC) and heavy (HC) antibody chains (arrowheads), three protein species (arrows) are found at high levels in the IP fraction. (B) Immunoprecipitation was performed with mAb206 and analysed by western blotting with L83. Comparable amounts of fraction IV (lane 1), unbound fraction (lane 2) and IP fraction (lane 3) were loaded on the gel. (C) L83 immunoprecipitates TPG activity. S1-S3 correspond to the IP supernatants obtained after the first, second and third cycle of IP, and B1-B3 to the bead fractions. Similar proportions of each fraction were tested for TPG activity (upper panel) and analysed by western blotting with L83 (lower panel). The position of p32 and of the antibody light chain are indicated by arrows. (D) Enrichment of PGs1 during TPG purification. Brain fractions I (initial supernatant) and II-IV [20x, 160x and 400x purified fractions, respectively, as described by Regnard et al. (Regnard et al., 1998)] were analysed by western blotting with L83. Equal amounts of proteins were loaded in each lane. (E) PGs1 mRNA expression profile. Total RNA from various mouse tissues were analysed by northern blotting and probed with a ³²P-labelled PGs1 cDNA ORF.

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