Schorderet S, Pearson R D, Vuocolo T, Eisemann C, Riding G A, Tellam R L
CSIRO Tropical Agriculture, Queensland, Australia.
Insect Biochem Mol Biol. 1998 Feb;28(2):99-111. doi: 10.1016/s0965-1748(97)00103-3.
The gut of most insects is lined with a semi-permeable peritrophic membrane (or peritrophic matrix) composed of chitin, proteoglycans and proteins. Despite the probable importance of the peritrophic membrane in facilitating the digestive process and protecting insects from invasion by micro-organisms and parasites, there has been little characterization of the specific components and their interactions within this acellular structure. Here we report the characterization of an integral peritrophic membrane glycoprotein, peritrophin-48, from the larvae of the fly Lucilia cuprina, a primary agent of cutaneous myiasis in sheep. Peritrophin-48 was purified from peritrophic membrane obtained by larval culture and its location within the peritrophic membrane determined by immuno-fluorescence and immuno-gold localizations. The cDNA coding for peritrophin-48 was cloned and sequenced. The deduced amino acid sequence codes for a protein of 375 amino acids containing an amino-terminal signal sequence followed by five similar, but non-identical domains, each approximately 65-70 amino acids in length and characterised by a specific register of six cysteines. The deduced amino acid sequence shows significant similarity to two other peritrophic membrane proteins, peritrophin-95 and peritrophin-44, from the same species. A reverse transcriptase-PCR approach indicated that there are several highly related peritrophin-48 genes expressed in each individual. Reverse transcriptase-PCR also demonstrated the expression of peritrophin-48 in all three larval instars and adults but not pupae or eggs. Peritrophin-48 was expressed only by the cardia and by the larval midgut. A simple structural model of a basic unit of a type 2 peritrophic membrane is presented.
大多数昆虫的肠道内衬有一层半透性的围食膜（或围食基质），其由几丁质、蛋白聚糖和蛋白质组成。尽管围食膜在促进消化过程以及保护昆虫免受微生物和寄生虫侵袭方面可能具有重要作用，但对于这种无细胞结构内的特定成分及其相互作用，却鲜有特征描述。在此，我们报告了从羊肤蝇蛆病的主要病原体——铜绿蝇幼虫中鉴定出一种完整的围食膜糖蛋白——围食蛋白-48。围食蛋白-48是从幼虫培养获得的围食膜中纯化出来的，其在围食膜内的位置通过免疫荧光和免疫金定位来确定。编码围食蛋白-48的cDNA被克隆并测序。推导的氨基酸序列编码一个375个氨基酸的蛋白质，该蛋白质含有一个氨基末端信号序列，随后是五个相似但不完全相同的结构域，每个结构域长度约为65 - 70个氨基酸，其特征是六个半胱氨酸的特定排列。推导的氨基酸序列与同一物种的另外两种围食膜蛋白——围食蛋白-95和围食蛋白-44具有显著相似性。逆转录酶-聚合酶链反应方法表明，每个个体中都有几个高度相关的围食蛋白-48基因表达。逆转录酶-聚合酶链反应还证明围食蛋白-48在所有三个幼虫龄期和成虫中表达，但在蛹或卵中不表达。围食蛋白-48仅由贲门和幼虫中肠表达。本文提出了2型围食膜基本单位的一个简单结构模型。
