Sugii S, Kabat E A, Shapiro M, Potter M
J Exp Med. 1981 Jan 1;153(1):166-81. doi: 10.1084/jem.153.1.166.
The immunochemical specificity of the combining sites of murine myeloma protein CAL20 TEPC1035 was studied by quantitative precipitin and precipitin inhibition assays. Myeloma protein CAL20 TEPC1035 precipitated with only three dextrans, B1355S4, B1498S, and B1501S, with high proportions of alpha(1 leads to 3) linkages, but not with any other dextrans, glycogen, and pullulan. Inhibition tests with various sugars show that the combining site of myeloma protein CAL20 TEPC1035 is most complementary to panose, a trisaccharide DGlc alpha(1 leads to 6)DGlc alpha(1 leads to 4)DGlc. Panose was 3.3 times more potent than a tetrasaccharide DGlc alpha(1 leads to 6)DGlc alpha(1 leads to 4)DGlc alpha(1 leads to 4)DGlc and 8, 23, 42, > 42 times more active than maltose, nigerose, isomaltose, and kojibiose, respectively. These findings were paralleled by their binding properties as determined by affinity electrophoresis. The association constants (Ka) of these three dextrans to myeloma protein CAL20 TEPC1035 ranged from 3.8 X 10(3) ml/g to 5.02 X 10(3) ml/g. The association constant of inhibitor (Kia) of panose was 8.19 X 10(3) M-1. Myeloma protein CAL20 TEPC1035 is an antidextran with specificity different from those of other murine myeloma antidextrans and from human antidextrans reported previously and its combining site size is at least as large as a trisaccharide. The binding constant of methyl alpha-D-glucoside (7.2 X 10(2)) was 73% of that of panose and comparable to that of myeloma protein W3129 (9.4 X 10(2)) with a cavity-type site and 600 times lower (1.6 X 10(0)) for QUPC52 with a groove type site, indicating that the terminal nonreducing residue is held in a cavity. Inhibition data with various alpha(1 leads to 4)-linked oligosaccharides also indicate that the internal portions of these inhibitors may react directly with a portion of the combining site. These findings suggest that myeloma antidextran CAL20 TEPC1035 has a partial cavity-type combining site in which the terminal nonreducing dGlc alpha(1 leads to 6) moiety is held in a cavity with the other two sugars forming a groove. However, oligosaccharides with one or more alternating [leads to 3DGlc alpha(1 leads to 6)DGlc alpha(1 leads to 3)DGlcl leads to] units with and without terminal nonreducing DGlc alpha(1 leads to 6) or DGLc alpha(1 leads to 3) side chains remain to be tested to determine whether structures known to be present in the three dextrans which precipitate CAL20 TEPC1035 may not prove to be more active than panose.
通过定量沉淀和沉淀抑制试验研究了小鼠骨髓瘤蛋白CAL20 TEPC1035结合位点的免疫化学特异性。骨髓瘤蛋白CAL20 TEPC1035仅与三种葡聚糖B1355S4、B1498S和B1501S沉淀，这些葡聚糖具有高比例的α(1→3)连接，但不与任何其他葡聚糖、糖原和支链淀粉沉淀。用各种糖类进行的抑制试验表明，骨髓瘤蛋白CAL20 TEPC1035的结合位点与潘糖最互补，潘糖是一种三糖DGlcα(1→6)DGlcα(1→4)DGlc。潘糖的效力比四糖DGlcα(1→6)DGlcα(1→4)DGlcα(1→4)DGlc高3.3倍，分别比麦芽糖、黑曲霉糖、异麦芽糖和曲二糖活跃8倍、23倍、42倍、>42倍。这些发现与其通过亲和电泳测定的结合特性相似。这三种葡聚糖与骨髓瘤蛋白CAL20 TEPC1035的缔合常数(Ka)范围为3.8×10³ml/g至5.02×10³ml/g。潘糖抑制剂的缔合常数(Kia)为8.19×10³M⁻¹。骨髓瘤蛋白CAL20 TEPC1035是一种抗葡聚糖，其特异性不同于其他报道的小鼠骨髓瘤抗葡聚糖和人抗葡聚糖，其结合位点大小至少与三糖一样大。α-D-葡萄糖苷甲基酯的结合常数(7.2×10²)是潘糖的73%，与具有腔型位点的骨髓瘤蛋白W3129(9.4×10²)相当，对于具有凹槽型位点的QUPC52则低600倍(1.6×10⁰)，这表明末端非还原残基位于一个腔内。用各种α(1→4)连接的寡糖进行的抑制数据也表明，这些抑制剂的内部部分可能直接与结合位点的一部分反应。这些发现表明，骨髓瘤抗葡聚糖CAL20 TEPC1035具有部分腔型结合位点，其中末端非还原dGlcα(1→6)部分位于腔内，另外两个糖形成一个凹槽。然而，具有一个或多个交替的[→3DGlcα(1→6)DGlcα(1→3)DGlc→]单元且有或没有末端非还原DGlcα(1→6)或DGLcα(1→3)侧链的寡糖仍有待测试，以确定已知存在于沉淀CAL20 TEPC1035的三种葡聚糖中的结构是否可能比潘糖更具活性。
