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. Author manuscript; available in PMC: 2010 Jul 23.
Published in final edited form as: Mol Cell. 2009 Jun 12;34(5):569–579. doi: 10.1016/j.molcel.2009.04.028

Figure 5. The isomerization of a single proline residue controls the assembly and secretion of heavy chains in vivo.

Figure 5

COS-1 cells were co-transfected with vectors encoding wild type MAK33 heavy chain (WT) or one of the three Pro to Ala mutants (P74A, P32A, or P34A) together with wild type light chain and BiP. Cells were metabolically labeled and both cell lysates (no subscript) and culture supernatants (subscript m) were immunoprecipitated with the indicated antisera (Ab). Precipitated proteins were separated by SDS-PAGE under non-reducing conditions and visualized by autoradiography. (B) The cell lysates and culture supernatants from (A) were divided in half, immunoprecipitated with the indicated antibodies, analyzed by SDS-PAGE under reducing conditions, and visualized with autoradiography. These data demonstrate that the failure of the P32A mutant to induce assembly and secretion is not because it is expressed poorly, as the signal for this mutant heavy chain is very similar to that of the wild type heavy chain.