An unusual crystal structure of ferric-enterobactin bound FepB suggests novel functions of FepB in microbial iron uptake

详细信息    查看全文

• 作者：Bingqing Li^a ; ^b ; ¹ ; ^{bingqingsdu@163.com" class="auth_mail" title="E-mail the corresponding author} ; Ning Li^b ; ¹ ; Yingying Yue^a ; Xiuhua Liu^b ; Yan Huang^b ; Lichuan Gu^b ; Sujuan Xu^b ; ^{xu_sujuan@sdu.edu.cn" class="auth_mail" title="E-mail the corresponding author}
• 关键词：FepB ; Enterobactin uptake ; Crystal structure ; Periplasmic binding protein
• 刊名：Biochemical and Biophysical Research Communications
• 出版年：2016
• 出版时间：23 September 2016
• 年：2016
• 卷：478
• 期：3
• 页码：1049-1053
• 全文大小：1517 K

文摘

Iron acquisition by siderophores is critical for the survival of most bacteria. Enterobactin is a kind of catechol siderophore that exhibits the highest affinity to iron atoms secreted by E. coli and several other species of Enterobacteriaceae. The periplasmic binding protein (PBP) FepB can transport ferric-enterobactin (Fe-Ent) from the outer membrane to the membrane-associated ATP-binding cassette transport system in E. coli. To elucidate this process, we solved the crystal structure of FepB in complex with Fe-Ent at a resolution of 1.8 Å. Consistent with previously reported NMR results, our crystal structure shows that, similar to the other type III PBPs, the FepB structure was folded with separated globular N- and C-termini linked by a long α-helix. Additionally, the structure showed that the Fe-Ent bound to the cleft between the N- and C-terminal domains. Exceptionally, FepB differs from the other known siderophore binding PBPs in that it forms a trimer by capturing four Fe-Ents that can each contribute to FepB trimerization. Dynamic light-scattering experiments are consistent with the structural observations and indicate that FepB forms a trimer in a Fe-Ent-dependent manner.