A Link between Integral Membrane Protein Expression and Simulated Integration Efficiency

• Closely related IMP sequences exhibit substantial differences in expression levels
• IMP expression levels are dependent upon the efficiency of membrane integration
• In distinct systems, mutations that improve IMP integration also improve expression
• Simulated IMP integration is used to design IMPs with enhanced expression

SummaryIntegral membrane proteins (IMPs) control the flow of information and nutrients across cell membranes, yet IMP mechanistic studies are hindered by difficulties in expression. We investigate this issue by addressing the connection between IMP sequence and observed expression levels. For homologs of the IMP TatC, observed expression levels vary widely and are affected by small changes in protein sequence. The effect of sequence changes on experimentally observed expression levels strongly correlates with the simulated integration efficiency obtained from coarse-grained modeling, which is directly confirmed using an in vivo assay. Furthermore, mutations that improve the simulated integration efficiency likewise increase the experimentally observed expression levels. Demonstration of these trends in both Escherichia coli and Mycobacterium smegmatis suggests that the results are general to other expression systems. This work suggests that IMP integration is a determinant for successful expression, raising the possibility of controlling IMP expression via rational design.

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