Frutiger S, Hughes G J, Hanly W C, Kingzette M, Jaton J C
J Biol Chem. 1986 Dec 15;261(35):16673-81.
Rabbit secretory components (SC) constitute a family of markedly heterogeneous glycoproteins which are released in the secretions as free SC or as SC bound to polymeric immunoglobulins. The aim of this work was to determine the region of the SC polypeptides which is involved in IgA binding. The high and the low Mr forms of free SC (or IgA-dissociated bound SC) and the native secretory IgA complex were subjected to limited tryptic digestion. Chemically characterized peptides ranging in apparent size from 15 to 20 kDa, depending upon the allotype, were shown to be necessary and sufficient for efficient noncovalent binding to IgA dimers (subclass g). These fragments encompass the amino-terminal first domain of SC, i.e. residues 1-126, when aligned with the predicted amino acid sequence from a cDNA clone encoding the rabbit polymeric Ig receptor (Mostov, K.E., Friedlander, M., and Blobel, G. (1984) Nature 308, 37-43). The high and the low Mr forms of SC exhibited the same relative affinity for IgA dimers, suggesting that the postulated internal deletion in the smaller polypeptide (Kühn, L. C., Kocher, H.-P., Hanly, W.C., Cook, L., Jaton, J.-C., and Kraehenbuhl, J.-P. (1983) J. Biol. Chem. 258, 6653-6659) does not impair the IgA dimer recognition function.
兔分泌成分（SC）构成了一个明显异质性糖蛋白家族，它们以游离SC或与聚合免疫球蛋白结合的SC形式分泌到分泌物中。这项工作的目的是确定SC多肽中参与IgA结合的区域。对游离SC（或IgA解离的结合SC）的高、低分子量形式以及天然分泌型IgA复合物进行了有限的胰蛋白酶消化。根据同种异型的不同，化学特征明确的肽段表观大小在15至20 kDa之间，已证明这些肽段对于与IgA二聚体（亚类g）进行有效的非共价结合是必要且充分的。当与编码兔聚合Ig受体的cDNA克隆预测的氨基酸序列比对时（莫斯托夫，K.E.，弗里德兰德，M.，和布洛贝尔，G.（1984）《自然》308，37 - 43），这些片段包含SC的氨基末端第一个结构域，即第1 - 126位氨基酸残基。SC的高、低分子量形式对IgA二聚体表现出相同的相对亲和力，这表明较小多肽中假定的内部缺失（库恩，L.C.，科赫尔，H.-P.，汉利，W.C.，库克，L.，雅顿，J.-C.，和克雷亨布尔，J.-P.（1983）《生物化学杂志》258，6653 - 6659）并不损害IgA二聚体识别功能。
