Cerenius L, Liang Z, Duvic B, Keyser P, Hellman U, Palva E T, Iwanaga S, Söderhäll K
Department of Physiological Botany, University of Uppsala, Sweden.
J Biol Chem. 1994 Nov 25;269(47):29462-7.
The prophenoloxidase activating system, an enzyme cascade present in arthropod blood, has been shown to be involved in defense and recognition reactions. This system is converted to its active form by fungal 1,3-beta-D-glucans through binding to a plasma protein, a 1,3-beta-D-glucan-binding protein. Here the molecular cloning and carbohydrate composition of the 1,3-beta-D-glucan-binding protein from the freshwater crayfish Pacifastacus leniusculus are reported. It is also demonstrated that this protein can act as an opsonin, stimulating phagocytic uptake of yeast particles by isolated blood cells. The deduced amino acid sequence of 1,339 residues shows no significant similarity to proteins with similar functions in other animals such as the mannan-binding and lipopolysaccharide-binding proteins present in mammals. However, a short sequence motif with similarity to the active site of microbial 1,3-1,4-beta-D-glucan 4-glucanohydrolases was found to occur twice in the 1,3-beta-D-glucan-binding protein.
酚氧化酶原激活系统是节肢动物血液中存在的一种酶级联反应，已被证明参与防御和识别反应。该系统通过与血浆蛋白（一种1,3-β-D-葡聚糖结合蛋白）结合，被真菌1,3-β-D-葡聚糖转化为活性形式。本文报道了淡水小龙虾美洲螯龙虾中1,3-β-D-葡聚糖结合蛋白的分子克隆和碳水化合物组成。还证明了该蛋白可作为调理素，刺激分离的血细胞对酵母颗粒的吞噬摄取。推导的1339个氨基酸残基的序列与其他动物中具有类似功能的蛋白质（如哺乳动物中存在的甘露糖结合蛋白和脂多糖结合蛋白）没有显著相似性。然而，在1,3-β-D-葡聚糖结合蛋白中发现了一个与微生物1,3-1,4-β-D-葡聚糖4-葡聚糖水解酶活性位点相似的短序列基序，出现了两次。
