Afp14 is involved in regulating the length of Anti‐feeding prophage (Afp)

The anti‐feeding prophage (Afp), a phage‐tail‐like particle that causes cessation of feeding in the New Zealand grass grub, Costelytra zealandica, is encoded by 18 open reading frames (afp1–18). C‐terminal truncations of afp14 resulted in shortened Afp particles, suggesting that Afp14 is involved in Afp length determination. We constructed an Afp assembly system (afp1–18), wherein Afp14 was truncated after the N‐terminal 88 residues. This construct, when expressed in trans in Escherichia coli expressing a N‐terminal 98‐amino acid Afp14 construct, yielded fully assembled Afp but no assembled Afp was detected in the case of a N‐terminal 96‐amino acid Afp14 construct. These results suggested that the 98 N‐terminal, amino acid residues of Afp14 is crucial for the initiation of Afp assembly via baseplate formation. Trans‐based expression of wild‐type afp14 resulted in Afp particles of varying lengths, all of which were shorter than the wild‐type Afp particle. On the other hand, similar expression of Afp14 harboring a C‐terminal extension (KLLEH₆) resulted in elongated Afp particles. This information, combined with bioinformatics data, allowed us to propose a model delineating the mechanism and role of Afp14 in the maturation of the Afp particle.