FIG. 5.

SP-D dodecamers induce greater aggregation than identical concentrations of trimeric SP-D subunits. P. carinii organisms were stripped of associated host proteins by use of glutathione and EDTA, and aggregation was monitored in the presence of recombinant dodecameric rat SP-D or mutant RrSP-Dser15,20, which assembles as trimeric single-arm structures (10 μg/ml each). EDTA (5 mM) was studied in parallel. P. carinii incubated in the dodecameric SP-D exhibited significantly greater aggregation than P. carinii incubated in equal concentrations of RrSP-Dser15,20. Shown are results of an experiment representative of four experimental runs. For statistical comparisons of aggregation conditions, see Results.