Institute for Molecular Bioscience, The University of Queensland, 306 Carmody Rd, St Lucia, QLD 4072, Australia.
Toxins (Basel). 2020 Dec 22;13(1):3. doi: 10.3390/toxins13010003.
Assassin bugs are venomous insects that prey on other arthropods. Their venom has lethal, paralytic, and liquifying effects when injected into prey, but the toxins responsible for these effects are unknown. To identify bioactive assassin bug toxins, venom was harvested from the red tiger assassin bug (), an Australian species whose venom has not previously been characterised. The venom was fractionated using reversed-phase high-performance liquid chromatography, and four fractions were found to cause paralysis and death when injected into sheep blowflies (). The amino acid sequences of the major proteins in two of these fractions were elucidated by comparing liquid chromatography/tandem mass spectrometry data with a translated venom-gland transcriptome. The most abundant components were identified as a solitary 12.8 kDa CUB (complement C1r/C1s, Uegf, Bmp1) domain protein and a 9.5 kDa cystatin. CUB domains are present in multidomain proteins with diverse functions, including insect proteases. Although solitary CUB domain proteins have been reported to exist in other heteropteran venoms, such as that of the bee killer assassin bug , their function is unknown, and they have not previously been reported as lethal or paralysis-inducing. Cystatins occur in the venoms of spiders and snakes, but again with an unknown function. Reduction and alkylation experiments revealed that the venom cystatin featured five cysteine residues, one of which featured a free sulfhydryl group. These data suggest that solitary CUB domain proteins and/or cystatins may contribute to the insecticidal activity of assassin bug venom.
猎蝽是一种有毒的昆虫，以其他节肢动物为食。它们的毒液在注入猎物时具有致命、麻痹和液化作用，但负责这些作用的毒素尚不清楚。为了鉴定生物活性猎蝽毒素，从红虎猎蝽（）中提取毒液，这是一种澳大利亚物种，其毒液以前没有被描述过。毒液使用反相高效液相色谱法进行分离，发现有四个馏分在注射到绵羊蝇（）中时会导致麻痹和死亡。通过将液相色谱/串联质谱数据与翻译的毒腺转录组进行比较，阐明了这两个馏分中主要蛋白质的氨基酸序列。两种馏分中含量最丰富的成分被鉴定为一种单一的 12.8 kDa CUB（补体 C1r/C1s、Uegf、Bmp1）结构域蛋白和一种 9.5 kDa 半胱氨酸蛋白酶抑制剂。CUB 结构域存在于具有多种功能的多结构域蛋白中，包括昆虫蛋白酶。尽管在其他半翅目昆虫毒液中已经报道存在单一的 CUB 结构域蛋白，例如蜜蜂杀手猎蝽的毒液，但它们的功能尚不清楚，并且以前也没有报道过它们具有致死或致麻痹作用。半胱氨酸蛋白酶抑制剂存在于蜘蛛和蛇的毒液中，但功能未知。还原和烷基化实验表明，毒液半胱氨酸蛋白酶抑制剂具有五个半胱氨酸残基，其中一个具有游离巯基。这些数据表明，单一的 CUB 结构域蛋白和/或半胱氨酸蛋白酶抑制剂可能有助于猎蝽毒液的杀虫活性。
