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. 2020 May 6;9:e55853. doi: 10.7554/eLife.55853

Figure 5. CALHM4 subunit and oligomeric arrangement.

(A) Ribbon representation of the CALHM4 subunit. Secondary structure elements are labeled and transmembrane α-helices are shown in unique colors. View of the transmembrane α-helices of (B), the CALHM4 decamer and (C), the volume regulated anion channel LRRC8A from the extracellular side. B-C, color code is as in A, transmembrane segments of one subunit are numbered. The general shape of a single subunit is indicated (B, trapezoid, C, oval). (D) Surface representation of the CALHM4 decamer. The view is from the outside. (E), Slice through the CALHM4 pore viewed from within the membrane. D, E, TM1 and the N-terminal α-helix NH are colored in red.

Figure 5.

Figure 5—figure supplement 1. Sequence and topology.

Figure 5—figure supplement 1.

Sequence alignment of the human CALHM paralogs CALHM1 (NP_001001412.3), CALHM2 (NP_057000.2), CALHM3 (NP_001123214.1), CALHM4 (NP_001353007.1), CALHM5 (NP_714922.1) and CALHM6 (NP_001010919.1). Identical residues are highlighted in green, secondary structure elements of CALHM4 are indicated above.
Figure 5—figure supplement 2. Features of the CALHM4 structure.

Figure 5—figure supplement 2.

(A) Molecular surface of the CALHM4 decamer viewed from within the membrane (left) and zoom into the highlighted region showing the interface between two subunits (right). Asterisk indicates location of a small fenestration on the surface between TM3 and TM4 of the same subunit. (B) Ribbon representation of TM1 and the N-terminal α-helix NH with side chains of hydrophobic residues facing the pore displayed as sticks. (C) Cα-trace of the extracellular region of CALHM4 with disulfide bridges shown as sticks and labeled. (D) Ribbon representation of TM2, the intracellular α-helix CLH and TM3. A, B, D, Transmembrane segments are colored as in Figure 5A and labeled.