Figure 4.

CATC Structures at Portal and Penton Vertices

(A) Sharpened CATC-binding penton vertex register density used to model CATC elements.

(B) Ribbon models of the CATC helix bundle in a coiled-coil arrangement of pORF64 and pORF19, two copies each.

(C and D) C1 reconstructions of the portal vertex (C) and penton vertex with one CATC occupancy (D), colored according to the key. Insets depict the colored C1 density within the Gaussian-filtered C1 map (gray), showing lower-resolution features and interactions. Connections between CATC helix bundles and the portal cap putatively formed by pORF19 head domains are visible in the filtered map (C, inset) and circled in black. One head domain of pORF19 is clearly visible in (D). Putative head domains of the second pORF19 copy in each CATC are circled in green (C and D, insets).

(E) Homology model of the pORF19 head domain docked into the C1 penton vertex density reveals a finger-like motif (∼aa 457–468) interacting with penton MCP.

(F) Superposition of the HSV-1 pUL25 head domain (PDB: 2F5U) with the docked pORF19 head domain homology model demonstrates conservation of the head domain structure between HSV-1 and KSHV.

(G and H) Ribbon model of pORF32 colored according to the domains in HSV-1 pUL17 (H).

(I and J) Schematics depicting Ta and Tc triplex orientations in the absence (I) and presence (J) of CATC at vertices. Insets (capsid interior view) show that the Ta Tri1 N-anchor retains a conserved orientation despite CATC-binding Ta’s 120° counterclockwise apical rotation.

See also Figures S3 and S5 and Video S3.