Sarcolectin: Complete purification for molecular cloning

A great variety of vertebrate cells contain detectable amounts of lectins, able to stimulate the initiation of cellular DNA synthesis. One of them, sa rcolectin (SCL) can block interferon (IFN) action, by inhibiting the synthe sis and the expression of the IFN dependent secondary proteins. As a result , the IFN-induced antiviral state is abolished in the cells, which likely f acilitates their replication. We identified a major 65 kDa and a minor 55 k Da protein, which could carry these cellular functions. Their purification, especially that of the 65 kDa, was difficult, because of the proximity of albumin. We devised therefore a two-step primary separation, followed by a four-step final purification, which are reported here. The purification was controlled by high pressure liquid chromatography (HPLC), SDS-PAGE electro phoresis and identified by Western blots. We found that only the minor 55 k Da protein can be considered as being sarcolectin, while the major 65 kDa b and results from the binding of some SCL molecules to albumin. The major bi ological functions, namely, stimulation of DNA synthesis and cell agglutina tion were preserved to the end of the last purification step. This work is requisite for establishing the molecular structure of SCL by recombinant DN A technology. (C) 1999 Societe francaise de biochimie et biologie moleculai re / Editions scientifiques et medicales Elsevier SAS.