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. 2019 Oct 16;5(10):eaax6497. doi: 10.1126/sciadv.aax6497

Fig. 4. Comparison of the TcA channels.

Fig. 4

(A) Cross sections of the TcA channels demonstrating the electrostatic Coulomb potential in the channel lumen of Pl-TcdA1, Xn-XptA1, Mm-TcdA4, and Yp-TcaATcaB at pH 7. Positively charged (14 kcal/mol) and negatively charged (−14 kcal/mol) residues are colored in blue and red, respectively. (B) Graph depicting the inner channel radius of Pl-TcdA1 (red), Xn-XptA1 (blue), Mm-TcdA4 (orange), and Yp-TcaATcaB (green). At the narrowest position of the Pl-TcdA1 prepore (Y2163, indicated by the dashed line), the diameter of the channel is 3.9 Å. In Xn-XptA1, Mm-TcdA4, and Yp-TcaATcaB, the channel diameter reaches only 8.2, 7.8, and 8.4 Å at the narrowest part, respectively. (C) Slice through the channel at the position of the Pl-TcdA1 channel constriction (Y2163).