Role of antifeeding prophage ( Afp ) protein Afp 16 in terminating the length of the Afp tailocin and stabilizing its sheath

• Published in: Molecular microbiology 2013-08, Vol.89 (4), p.702-714
• Main Authors: Rybakova, Daria, Radjainia, Mazdak, Turner, Adrian, Sen, Anindito, Mitra, Alok K., Hurst, Mark R. H.
• Format: Article
• Language: English
• ISSN: 0950-382X; 1365-2958
• DOI: 10.1111/mmi.12305

The S erratia entomophila antifeeding prophage Afp , forms a phage‐tail‐like particle that acts on the N ew Z ealand grass grub, C ostelytra zealandica with a 3‐day LD 50 of approximately 500 Afp particles per larva. Genes ( afp1–18 ) encoding components of Afp were expressed and their products purified allowing morphological assessment of the products by transmission electron microscopy ( TEM ). Expression of afp1–15 resulted in the formation of a non‐sheathed structure termed the tube‐baseplate complex or TBC , composed of an irregular‐length tube attached to a baseplate with associated tail fibres. Expression of afp1–16 produced mature, normal‐length Afp particles, whereas coexpression of afp16 with afp1–15 in trans resulted in the formation of aberrant Afp particles of variable lengths. A C ‐terminally truncated Afp 16 mutant resulted in a phenotype intermediate between mature Afp and TBC . The addition of purified Afp 16 to Afp unravelled by acidic treatment resulted in the formation of shorter tubes when specimen pH was adjusted to 7 than those formed in the absence of Afp 16. Analysis of TEM images of purified Afp 16 revealed a hexameric ring‐like structure similar to that formed by gp3 of phage T 4 and gpU of phage λ. Our results suggest that Afp 16 terminates tube elongation and is involved in sheath formation.