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The molecular mechanisms for the initial recognition and subsequent internalization of food and unicellular pathogens by phagocytes are incompletely understood We have hypothesized that a surface-exposed, glycosylated I30 kDa protein, gp130, that 1s concentrated on the plasma membrane and found In phagosomes, has a role In phagocytosis by D. discoideum amoebae. GpI30 appears to have a cytoskeletal association and has extracellular domains susceptible to proteolytic digestion. It is tightly bound to the plasma membrane probably via a carboxyterminal hydrophobic anchor predicted from the cDNA. Gp130 may be the same as a similarly sized protein, gp126, that was implicated as a phagocytosis receptor and a cell adhesion protein during starvation-induced development (Chadwick et al, 1984, Nature, 307, 646) Primers for DNA polymerase chain reaction (PCR) were designed from internal amino acid sequences of proteolyzed gp130 and its gene sequence was determined by PCR and cycle sequencing.