Amylase-binding protein B of Streptococcus gordonii is an extracellular dipeptidyl-peptidase
Amylase-binding protein B of Streptococcus gordonii is an extracellular dipeptidyl-peptidase
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DOI：
10.1128/iai.00186-08
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发表时间：
2008-10-01
影响因子：
3.1
通讯作者：
Scannapieco, Frank A.
中科院分区：
文献类型：
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作者：
Chaudhuri, Biswendu;Paju, Susanna;Scannapieco, Frank A.
口腔链球菌通过两种淀粉酶结合蛋白AbpA和AbpB与唾液淀粉酶相互作用。基于序列分析，20-kDa AbpA蛋白是S. gordonii，而82-kDa的AbpB蛋白似乎与其他细菌二肽酶共享序列同源性。本研究的目的是验证AbpB的肽酶活性，并进一步探讨其潜在的功能。克隆了abpB基因，并在大肠杆菌中表达并纯化了组氨酸标记的AbpB（His-AbpB）。在淀粉酶配体结合试验中验证了其淀粉酶结合活性，并与抗AbpB抗体验证了其交叉反应性。重组His-AbpB和部分纯化的天然AbpB显示二肽酶活性和降解人VI型胶原和纤维蛋白原，但不唾液淀粉酶。唾液淀粉酶不仅能从S.戈登氏菌上清液。由于变形链球菌也释放Gtf酶，这些酶也可能参与多菌种菌斑相互作用，因此变形链球菌的作用。gordonii AbpB对S.还测试了变形杆菌Gtf-B活性。唾液淀粉酶和/或His-AbpB引起S.变形杆菌Gtf-B蔗糖酶活性和转移酶活性的3至6倍增加。酶联免疫吸附试验验证了His-AbpB和淀粉酶与Gtf-B的相互作用。总之，AbpB表现出蛋白水解活性，并与Gtf活性相互作用和调节Gtf活性。这些活动可能有助于解释AbpB在S.戈登口腔殖民。
The oral commensal bacterium Streptococcus gordonii interacts with salivary amylase via two amylase-binding proteins, AbpA and AbpB. Based on sequence analysis, the 20-kDa AbpA protein is unique to S. gordonii, whereas the 82-kDa AbpB protein appears to share sequence homology with other bacterial dipeptidases. The aim of this study was to verify the peptidase activity of AbpB and further explore its potential functions. The abpB gene was cloned, and histidine-tagged AbpB (His-AbpB) was expressed in Escherichia coli and purified. Its amylase-binding activity was verified in an amylase ligand binding assay, and its cross-reactivity was verified with an anti-AbpB antibody. Both recombinant His-AbpB and partially purified native AbpB displayed dipeptidase activity and degraded human type VI collagen and fibrinogen, but not salivary amylase. Salivary amylase precipitates not only AbpA and AbpB but also glucosyltransferase G (Gtf-G) from S. gordonii supernatants. Since Streptococcus mutans also releases Gtf enzymes that could also be involved in multispecies plaque interactions, the effect of S. gordonii AbpB on S. mutans Gtf-B activity was also tested. Salivary amylase and/or His-AbpB caused a 1.4- to 2-fold increase of S. mutans Gtf-B sucrase activity and a 3-to 6-fold increase in transferase activity. An enzyme-linked immunosorbent assay verified the interaction of His-AbpB and amylase with Gtf-B. In summary, AbpB demonstrates proteolytic activity and interacts with and modulates Gtf activity. These activities may help explain the crucial role AbpB appears to play in S. gordonii oral colonization.