期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2002
卷号：99
期号：26
页码：16642-16647
DOI：10.1073/pnas.262659699
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Bacterial binding protein-dependent ATP binding cassette (ABC) transporters facilitate uptake of essential nutrients. The crystal structure of Escherichia coli BtuF, the protein that binds vitamin B12 and delivers it to the periplasmic surface of the ABC transporter BtuCD, reveals a bi-lobed fold resembling that of the ferrichrome binding protein FhuD. B12 is bound in the "base-on" conformation in a deep cleft formed at the interface between the two lobes of BtuF. A stable complex between BtuF and BtuCD (with the stoichiometry BtuC2D2F) is demonstrated to form in vitro and was modeled using the individual crystal structures. Two surface glutamates from BtuF may interact with arginine residues on the periplasmic surface of the BtuCD transporter. These glutamate and arginine residues are conserved among binding proteins and ABC transporters mediating iron and B12 uptake, suggesting that they may have a role in docking and the transmission of conformational changes.
