Recombinant ADAMTS13. (A) The indicated ADAMTS13 variants were expressed in 293T cells, purified and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and staining with InstantBlue (Expedion, San Diego, CA). Size in kilodaltons is indicated for standards. (B) Pigeon ADAMTS13 constructs with or without the propeptide were expressed in 293T cells in the presence or absence of the furin inhibitor decanoyl-Arg-Val-Lys-Arg-chloromethane (50 µM), as indicated. Samples of conditioned medium were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting with anti-6xHis Ab. The positions of proADAMTS13 and mature ADAMTS13 are indicated.