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. Author manuscript; available in PMC: 2014 Dec 1.
Published in final edited form as: Biochim Biophys Acta. 2013 Dec;1828(12):2873–2885. doi: 10.1016/j.bbamem.2013.03.032

Figure 5.

Figure 5

Residues in SREBP-2 important for cleavage by S2P and a model for partial α-helix unwinding of SREBPs. A) Effect of substitutions in TMS 1 of SREBP-2 on cleavage by S2P. Residues 478–502 include four residues (blue) preceding TMS 1 (black). The cleavage site is indicated by an arrow. Single-residue substitutions having no effect (green) or reducing cleavage (orange) are shown immediately above and below the sequence, respectively. Multi-residue substitutions having no effect (green) or abolishing cleavage (red) are separated from the sequence by lines that indicate which residues were substituted. B) Model for partial α-helix unwinding of SREBPs. Left) S1P cleaves the lumenal loop of an SREBP (see Fig. 1A for domain abbreviations). Right) Separation of the two TMSs is proposed to allow the N-terminal part of TMS 1 to unwind, exposing the cleavage site to the cytosolic face of the membrane for cleavage by S2P.