Affinity purification of a 70K protein, a membrane protein relevant to sexual cell fusion in Dictyostelium discoideum

Sexual cell fusion occurs between HM1 and NC4, heterothallic strains in Dictyostelium discoideum. A membrane component of HM1 cells with a molecular mass of 70 kDa (70K protein) has been shown to be implicated in cell fusion (Urishihara et al. (1988) Cell Differ. Dev. 25, 81–88). In the present study, 70K protein was partially purified using affinity Sepharose on which membrane proteins of NC4 cells were immobilized. Through this process, involvement of Ca²⁺ in the interaction of 70K protein with its receptor was suggested. Lectin staining of partially purified 70K protein indicated it to be a glycoprotein containing d-mannose and/or d-glucose residues.