Fig. 4: Cryo-EM structures of the isolated Wza translocon and Wzc octamer.
From: Molecular insights into the capsular polysaccharide transporter Wza-Wzc complex
a Cryo-EM density map of the Wza translocon resolved with C8 symmetry. The EM map is colored in purple. b Structural model of the Wza translocon. The model is colored in purple. c Structural comparison of Wza before (purple) and after (tomato red) complex formation with Wzc, illustrating its conformational stability. d Cryo-EM map of the isolated E. coli K12 WzcK504M octamer obtained by C1 reconstruction. The EM density map of Conf i protomers is colored light green. The EM density map of Conf ⅱ protomers is colored in yellow-green. e Cross-sectional view showing the inner membrane cavity of E. coli K12 WzcK504M sealed by the HA domains in Conf ⅰ of WzcK504M. f, g Structural model of E. coli K12 WzcK540M octamer generated based on the C1-reconstructed EM density map. Conf i protomers are colored light green; Conf ⅱ protomers are yellow green. Only the HA forearm of the Conf ⅱ protomer is resolved. h Model of E. coli K30 WzcK540M (C1 symmetry; PDB: 7NII)13. The Wzc protomers corresponding to classes 1–3 are shown in gold, dark green, and red, respectively. i Superimposition of E. coli K12 Conf ⅰ WzcK540M and E. coli K30 WzcK540M (class 3) protomers reveals vertical displacements of the JR domain. The hydrophobic helix (residues 118–129) within the JR domain lies near the inner membrane in the class 3 conformation, suggesting membrane association. Upward movement of the JR domain during conformational transitions (class 3 to Conf ⅰ) likely facilitates its dissociation from the membrane, potentially contributing to the CPS translocation. a.a. (amino acids).
