Biology Department Seminar

Approximately 80% of membrane proteins with known structures exist as oligomers when crystallized. However, it is not yet clear how membrane protein oligomers assemble in cell membrane. We investigated the trimerization process of Escherichia coli multidrug transporter AcrB. AcrB is an obligate trimer, existing and operating exclusively in the trimeric form. It is not clear if an individual subunit folds into a monomeric form first followed by association, or if association occurs simultaneously with subunit folding. To answer this question, we investigated the feasibility of creating folded monomeric AcrB mutant. The existence of well-folded monomers in the cell membrane would be an evidence of the latter. In addition, we examined the co-assembly of AcrB mutants co-expressed in the same cell to determine if oligomerization in vivo is a random process. Our results provide novel insights into the dynamic assembly and equilibration process of obligate homo-oligomeric membrane proteins.