Proposed modes of action of mOSM-RFPs. (A) Arrangement of the domains of mOSMR and mgp130 in analogy to the closely related LIF receptor complex . The green line depicts the linker in the functional inhibitors mOSM-RFP and mOSM-RFP+D1, the red line depicts the required linker for functional inverted mOSM-RFPs. (B) Schematic representation of a heterotetrameric complex of i-mOSM-RFP or i-mOSM-RFP+D1 with mOSM. Note that in three dimensions the heterotetrameric complex can be arranged in a way that the linkers are much shorter.