Binding of salivary agglutinin to IgA
Binding of salivary agglutinin to IgA
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DOI：
10.1042/bj20040265
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发表时间：
2004-10-01
影响因子：
4.1
通讯作者：
Amerongen, AVN
中科院分区：
文献类型：
--
作者：
Ligtenberg, AJM;Bikker, FJ;Amerongen, AVN
唾液凝集素（SAG）与来自肺部的gp-340（糖蛋白-340）相同，由DMBTI编码（在恶性脑肿瘤中缺失1）。它是SRCR（富含半胱氨酸的清道夫受体）超家族的成员，包含14个SRCR结构域，其中13个结构域高度相似。唾液中的SAG部分与IgA结合，这可能是细菌结合所必需的。本研究的目的是表征纯化的SAG与IgA的结合。SAG结合多种蛋白，包括血清和分泌性IgA，来自兔、羊、猪和小鼠的碱性磷酸酶结合的igg，以及乳铁蛋白和白蛋白。IgA与SAG的结合是钙依赖的，并被0.5 M KCI抑制，这表明其中涉及静电相互作用。SAG减少后，IgA的结合被破坏，表明该蛋白片段参与了结合。为了进一步确定IgA在SAG上的结合域，我们设计和合成了一些基于共识的SRCR结构域和SRCR穿插结构域的肽。ELISA与IgA的结合研究表明，在包含109个氨基酸的SRCR结构域的18-33氨基酸（QGRVEVLYRGSWGTVC）中，只有1个肽与IgA结合。这个结构域与参与与细菌结合的SAG结构域相同。尽管有类似的结合位点，但IgA并没有抑制变形链球菌与SAG或肽的结合。这些结果表明，IgA与SAG的结合是由SRCR结构域上的肽序列特异性介导的。
SAG (salivary agglutinin), which is identical to gp-340 (glycoprotein-340) from the lung, is encoded by DMBTI (deleted in malignant brain tumours 1). It is a member of the SRCR (scavenger receptor cysteine-rich) superfamily and contains 14 SRCR domains, 13 of which are highly similar. SAG in saliva is partially complexed with IgA, which may be necessary for bacterial binding. The goal of the present study was to characterize the binding of purified SAG to IgA. SAG binds to a variety of proteins, including serum and secretory IgA, alkaline phosphatase-conjugated IgGs originating from rabbit, goat, swine and mouse, and lactoferrin and albumin. Binding of IgA to SAG is calcium dependent and is inhibited by 0.5 M KCI, suggesting that electrostatic interactions are involved. Binding of IgA was destroyed after reduction of SAG, suggesting that the protein moiety is involved in binding. To pinpoint further the binding domain for IgA on SAG, a number of consensus-based peptides of the SRCR domains and SRCR interspersed domains were designed and synthesized. ELISA binding studies with IgA indicated that only one of the peptides tested, comprising amino acids 18-33 (QGRVEVLYRGSWGTVC) of the 109-amino-acid SRCR domain, exhibited binding to IgA. This domain is identical to the domain of SAG that is involved in binding to bacteria. Despite this similar binding site, IgA did not inhibit binding of Streptococcus mutans to SAG or peptide. These results show that the binding of IgA to SAG is specifically mediated by a peptide sequence on the SRCR domains.