Fig. 6: Alteromonas phage chaperones resemble intramolecular chaperone domains used by other phage RBPs.

a A5 gp9 and V22 gp27 chaperones closely resemble the C-terminal intramolecular chaperone domains (IMC; magenta) that mediate trimerization and maturation of phage RBPs (grey surface structures shown) prior to autoproteolytic cleavage (after the serine (Ser) residues highlighted in (c)) and removal from the mature RBP. Representative IMC-containing RBPs are shown for the tailspike of K1F (modeled here using PDB IDs: 3GW6 and 1V0E)⁴⁴ and the tail fiber of E. coli phage T5 (PDB ID: 4UW8)⁴³. b Homotrimers of gp9 and gp27 were predicted by AlphaFold-Multimer to form similar arrangements as the IMC complexes of the K1F TSP and T5 tail fiber. c Ribbon representations of A5 gp9, V22 gp27, and isolated IMC domains of the K1F tailspike and T5 tail fiber colored from the N- to C- terminus (blue to red) with approximate lengths of the β-hairpin domains indicated. d AlphaFold-Multimer predictions of the heterohexameric tail fiber (both truncated to the knob domain) and chaperone (full-length) complexes formed by A5 (gp8 and gp9) and V22 (gp26 and gp27). Highlighted is a six-strand β-sheet generated by tail fiber (β1, β4, β8) and chaperone (β1, β2, β3) β-strands formed between each tail fiber and chaperone pair in both the A5 and V22 complex. Model confidence scores are provided in Table S1. Source Data (pdb files) are provided as a Source Data file.