Li Ying, Chen Xiaobao, Jia Nan, Zhang Xuan, Zang Jianye
Hefei National Laboratory for Physical Sciences at Microscale CAS Center for Excellence in Biomacromolecules, Collaborative Innovation Center of Chemistry for Life Sciences, and School of Life Sciences, University of Science and Technology of China, 96 Jinzhai Road, Hefei, 230026, Anhui, People's Republic of China.
Key Laboratory of Structural Biology, Chinese Academy of Sciences, Hefei, 230027, Anhui, People's Republic of China.
Biotechnol Lett. 2017 Sep;39(9):1413-1423. doi: 10.1007/s10529-017-2374-6. Epub 2017 Jun 26.
To identify and characterize staphylococcus exotoxin-like (SET) protein Set11 from Staphylococcus aureus Mu50 strain and its possible targets proteins from human blood/serum.
Set11 is a member of the staphylococcal superantigen-like (SSL) proteins (also called Staphylococcus exotoxin-like (SET) proteins) family that is found in staphylococcal strain Mu50. Its structure and function, however, remain unknown. We performed bioinformatics analysis of Set11: it had 90% sequence identity to SSL7 in NCTC 8325 strain, indicating Set11 is a SSL7 ortholog. SSL7 in ATCC 12598 strain binds complement C5 to inhibit complement system. To investigate if Set11 binds C5, we made the homology model of Set11 and the Set11-C5 complex model based on SSL7 and SSL7-C5 structures, respectively. Structural analysis and sequence alignment reveal that the residues in SSL7 involved in C5 binding are conserved in Set11, indicating C5 as the potential target for Set11. To identify new targets of Set11, we cloned, expressed and purified Set11 and performed CNBr-pull down combined mass spectrum assays using human blood and serum.
We identified Set11 as the ortholog of SSL7 and determined C5, fibronectin 1 isoform 3 preproprotein, albumin, alpha-1-microglobulin precursor and complement C3 processor as the potential target proteins for Set11, indicating new functions of Set11/SSL7.
从金黄色葡萄球菌Mu50菌株中鉴定并表征葡萄球菌外毒素样（SET）蛋白Set11及其在人血液/血清中的可能靶蛋白。
Set11是葡萄球菌超抗原样（SSL）蛋白（也称为葡萄球菌外毒素样（SET）蛋白）家族的成员，存在于葡萄球菌Mu50菌株中。然而，其结构和功能仍不清楚。我们对Set11进行了生物信息学分析：它与NCTC 8325菌株中的SSL7有90%的序列同一性，表明Set11是SSL7的直系同源物。ATCC 12598菌株中的SSL7结合补体C5以抑制补体系统。为了研究Set11是否结合C5，我们分别基于SSL7和SSL7-C5结构构建了Set11的同源模型和Set11-C5复合物模型。结构分析和序列比对表明，SSL7中参与C5结合的残基在Set11中保守，表明C5是Set11的潜在靶标。为了鉴定Set11的新靶标，我们克隆、表达并纯化了Set11，并使用人血液和血清进行了CNBr下拉结合质谱分析。
我们鉴定出Set11是SSL7的直系同源物，并确定C5、纤连蛋白1异构体3前体蛋白、白蛋白、α-1-微球蛋白前体和补体C3加工蛋白是Set11的潜在靶蛋白，表明了Set11/SSL7的新功能。
