Abstract
We isolated mutants defective in aggregation (aggregation-less) by mutagenizing the "double-bypass" mutant HG592 of Dictyostelium discoideum as the parental strain. One of the mutants expressed the contact site A glycoprotein with an apparent molecular weight of 80 × 103 on the cell surface in the normal developmental stage and retained EDTA-stable cell contact as well as EDTA-sensitive cell contact. However, the mutant failed to aggregate on agar plates with bacteria. This mutant was designated HG700. We could not identify any differences between this mutant and the parental strain in levels of adenylate cyclase or extracellular phosphodiesterase activity, or in its chemotaxis toward cAMP. The mutant had greatly decreased the incorporation of [35S] sulfate into the particulate fractions of the cells starved for 6 h. This sug-gests that the modification by sulfation may crucially affect the mechanism of cell aggregation.
