Figure 5. Ii–CS cross-links to form a complex whose molecular mass is consistent with Ii trimerization.

Ltk− cells stably transfected with the p31EA construct were labelled with [³H]leucine or ³⁵SO₄ for 1.5 h and lysed in the absence (−) or presence (+) of DSP. Lysates were immunoprecipitated with P4H5 (anti-Ii), treated without (A) or with (B) the reducing agent 2-mercaptoethanol to reduce the cross-linker DSP and separated on 5–10% gradient gels. Monomeric, dimeric and trimeric conventional Ii and molecular-mass markers are indicated on the left (sizes in kDa), and Ii–CS complexes are indicated on the right.