Fig. 3. Identification of procathepsin L in SFCM from EOMA cell cultures. (A) Coomassie Blue staining of SFCM (lane 1) and single fractions of test purifications with Q- and SP-Sepharose columns. N–terminal sequencing of the 38 kDa band in the 250 mM NaCl eluate of SP-Sepharose (S250) gave the sequence TPKFDQTF-A, corresponding to the N–terminus of murine procathepsin L. (B) The fractions from (A) were probed with [¹²⁵I]LHVS-PhOH and analyzed by SDS–PAGE and autoradiography. Specific labeling was found in the flow-through (FT) of Q-Sepharose and in the S250 fraction. (C) Fractions from (A) and (B) were probed with an antibody against murine procathepsin L (anti-pro Cat L). Some processing of procathepsin L results from repeated freezing and thawing.