Innovative Farm Systems, AgResearch, Lincoln Research Centre, Private Bag 4749, Christchurch 8140, New Zealand.
Mol Microbiol. 2013 Aug;89(4):702-14. doi: 10.1111/mmi.12305. Epub 2013 Jul 11.
The Serratia entomophila antifeeding prophage Afp, forms a phage-tail-like particle that acts on the New Zealand grass grub, Costelytra zealandica with a 3-day LD50 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 Afp16 mutant resulted in a phenotype intermediate between mature Afp and TBC. The addition of purified Afp16 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 Afp16. Analysis of TEM images of purified Afp16 revealed a hexameric ring-like structure similar to that formed by gp3 of phage T4 and gpU of phage λ. Our results suggest that Afp16 terminates tube elongation and is involved in sheath formation.
食虫沙雷氏菌抗取食噬菌体 Afp 形成一种噬菌体尾状颗粒，对新西兰草地蟋蟀 Costelytra zealandica 具有 3 天的 LD50，约为每只幼虫 500 个 Afp 颗粒。编码 Afp 成分的基因（afp1-18）被表达，其产物被纯化，允许通过透射电子显微镜（TEM）对产物进行形态评估。afp1-15 的表达导致形成一种无鞘结构，称为管-基板复合物或 TBC，由附着在基板上的不规则长度管和相关尾纤维组成。afp1-16 的表达产生成熟的、正常长度的 Afp 颗粒，而 afp16 与 afp1-15 在反式共表达导致形成长度可变的异常 Afp 颗粒。C 端截断的 Afp16 突变体导致表型在成熟 Afp 和 TBC 之间。将纯化的 Afp16 添加到酸性处理解开的 Afp 中，当标本 pH 值调整为 7 时，形成的短管比在没有 Afp16 的情况下形成的短管短。对纯化的 Afp16 的 TEM 图像分析表明，它形成了一种类似于噬菌体 T4 的 gp3 和噬菌体 λ 的 gpU 形成的六聚体环状结构。我们的结果表明，Afp16 终止管伸长并参与鞘形成。
