Biochemical analysis of the recombinant proα2(V) chains produced in HEK-293 cells. (a) 6% SDS-PAGE analysis of cell media from untransfected cells (lane 1) and from cells transfected with human proα2(V) construct (lanes 2–5) under unreduced (lanes 1, 2) or reduced (lanes 3, 4, 5) conditions. Transfected cells media were incubated without (lane 4) or with (lane 5) pepsin before SDS-PAGE analysis. (b) Digestion with bacterial collagenase: transfected cell media were incubated without (lane 1) or with (lanes 2, 3) collagenase before 12% SDS-PAGE analysis under reduced (lanes 1, 2) or unreduced (lane 3) conditions. (c) Digestion with BMP-1: 12% SDS-PAGE patterns of transfected cells media digested (lane 2) or not (lane 1) with BMP-1. Gels (a) and (b) were stained with Coomassie blue whereas gel (c) was silver stained. Left, molecular mass standards expressed in kDa. NT: not transfected, proα2(V): transfected with proα2(V) construct, DTT: dithiothreitol, Cpro: C-propeptide, Npro: N-propeptide, BMP-1: Bone Morphogenetic Protein 1.