Kang Y, Kulakosky P C, van Antwerpen R, Law J H
Department of Biochemistry, University of Arizona, Tucson 85721, USA.
Insect Biochem Mol Biol. 1995 Apr;25(4):503-10. doi: 10.1016/0965-1748(94)00090-l.
Sequestration of the blue biliprotein, insecticyanin, into developing oocytes of the hawkmoth, Manduca sexta was investigated. Immunodiffusion assays revealed that insecticyanin concentration in mature eggs (29.6 microM) is slightly higher than that in hemolymph (25.8 microM). The endocytotic uptake of insecticyanin was visualized at the light microscopic level using autoradiography. Uptake of 125I-insecticyanin by isolated oocytes was saturable. Analysis of in vitro uptake data estimated that the value of K(uptake) (insecticyanin concentration at half-maximal uptake rate) is 4.2 microM and that the Vmax (maximum rate of uptake) is 1 pmol follicle-1 h-1. Labeled insecticyanin was shown to bind to sonicated follicle membranes with high specificity and affinity. The KD (equilibrium dissociation constant) and the Bm (total number of binding sites per follicle), were estimated as 4 x 10(-8) M and 8 x 10(7) respectively. Competition studies showed that binding of labeled insecticyanin to oocyte membranes was blocked by excess amounts of unlabeled insecticyanin but not by lipophorin and vitellogenin of M. sexta. Additional membrane binding experiments demonstrated that receptors for insecticyanin are only present in the oocytes membranes, not in fat body or gut tissue.
对蓝色胆色素蛋白昆虫蓝蛋白在烟草天蛾发育中的卵母细胞中的隔离情况进行了研究。免疫扩散分析表明，成熟卵中昆虫蓝蛋白的浓度（29.6微摩尔）略高于血淋巴中的浓度（25.8微摩尔）。使用放射自显影技术在光学显微镜水平观察到了昆虫蓝蛋白的内吞摄取。分离的卵母细胞对125I - 昆虫蓝蛋白的摄取具有饱和性。对体外摄取数据的分析估计，K(摄取)（摄取速率达到最大值一半时的昆虫蓝蛋白浓度）的值为4.2微摩尔，Vmax（最大摄取速率）为1皮摩尔·卵泡-1·小时-1。标记的昆虫蓝蛋白显示出与超声处理的卵泡膜具有高度特异性和亲和力的结合。KD（平衡解离常数）和Bm（每个卵泡的结合位点总数）分别估计为4×10(-8) M和8×10(7)。竞争研究表明，标记的昆虫蓝蛋白与卵母细胞膜的结合被过量的未标记昆虫蓝蛋白阻断，但未被烟草天蛾的脂转运蛋白和卵黄原蛋白阻断。额外的膜结合实验表明，昆虫蓝蛋白的受体仅存在于卵母细胞膜中，而不存在于脂肪体或肠道组织中。
