Specificity of R58 and L59 antibodies. (a) Schematic structure of a GST- rhLTGF-β1 protein generated in bacteria and a commercial rhLAP β1 generated in insect cells. The PLK cleavage site is indicated by arrowhead. (b-e) GST-LTGF-β1/rhLAP β1was incubated with/without PLK or PLN for 45 min at 37°C, and thereafter equal amounts of samples containing either 50 ng GST-rhLTGF-β1 or 500 ng rhLAP β1 were subjected to each lane in SDS-PAGE under reducing conditions followed by Western blot analyses using R58/L59 antibodies (b, d, respectively). Membranes used in panels b and d were reprobed with monoclonal (c) or polyclonal (e) anti-LAP antibodies. Lanes 1, intact GST-rhLTGF-β1 or rhLAP-β1; lanes 2, PLK digested GST-rhLTGF-β1 or rhLAP-β1; lanes 3, PLK; lane 4, PLN digested GST-rhLTGF-β1 or rhLAP-β1; lane 5, PLN. Representative results from three independent experiments with a similar result are shown.