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. Author manuscript; available in PMC: 2014 Sep 15.
Published in final edited form as: Annu Rev Cell Dev Biol. 2011 Jul 21;27:25–56. doi: 10.1146/annurev-cellbio-092910-154125

Figure 2.

Figure 2

Assay systems used to probe sequence determinants of insertion and topology. (a) An integral membrane protein (IMP) is targeted to and docked at the translocon via earlier transmembrane domains (gray), and a later test sequence (red) is measured for insertion. The relative amounts of the two possible outcomes are assayed, typically by a modification such as glycosylation. (b) A single-spanning IMP and its flanking sequences are systematically varied, and the substrate is presented to the translocation apparatus. The final topology achieved by this combination targeting-translocation-insertion system is assayed, again typically using glycosylation as a readout.