Galli J, Wieslander L
Department of Cell and Molecular Biology, Medical Nobel Institute, Karolinska Institutet, Stockholm, Sweden.
J Biol Chem. 1993 Jun 5;268(16):11888-93.
The secretion from the salivary glands in the dipteran Chironomus tentans has previously been shown to contain secretory proteins encoded by a set of related genes belonging to the Balbiani ring multigene family. Here we describe the characterization of a gene for an additional secretory protein of a novel type. This sp240/420 gene is built from virtually identical 477-base pair repeats organized in tandem. The gene exhibits extensive length polymorphism since allelic length variants with from 12 to 22 repeats were recorded. Antibodies have been raised against the gene product, and it is shown also that the protein varies in size between 240 and 420 kDa. The protein is rich in serine and threonine residues (30%) and has N-linked carbohydrate chains, presumably on each repeat. Despite careful preparation of the gland lumen proteins, the sp240/420 protein was found to form protein ladders of regularly degraded protein, suggesting that this degradation occurs naturally in the salivary glands. Although all previously characterized salivary gland secretory protein genes in C. tentans belong to the same multigene family, the sp240/420 gene appears to represent a novel, unrelated type of repetitive gene. The chromosomal location of the gene was mapped and was found to reside in region 17 on chromosome I.
双翅目昆虫摇蚊的唾液腺分泌物先前已被证明含有由一组属于巴尔比亚尼环多基因家族的相关基因编码的分泌蛋白。在此，我们描述了一种新型额外分泌蛋白的基因特征。这个sp240/420基因由几乎相同的477个碱基对的重复序列串联组成。该基因表现出广泛的长度多态性，因为记录到了具有12至22个重复序列的等位基因长度变体。已经制备了针对该基因产物的抗体，并且还表明该蛋白质的大小在240至420 kDa之间变化。该蛋白质富含丝氨酸和苏氨酸残基（30%），并且具有N-连接的碳水化合物链，可能在每个重复序列上。尽管对腺腔蛋白进行了仔细的制备，但发现sp240/420蛋白形成了规则降解蛋白的蛋白梯，这表明这种降解在唾液腺中自然发生。尽管先前在摇蚊中鉴定的所有唾液腺分泌蛋白基因都属于同一个多基因家族，但sp240/420基因似乎代表了一种新型的、不相关的重复基因类型。该基因的染色体定位已被绘制出来，发现它位于第一号染色体的17区。
