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Asymmetric Conformational Flexibility in the ATP-Binding Cassette Transporter HI1470/1 |
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| Authors: | Jingwei Weng Kangnian Fan |
| Institution: | † Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Department of Chemistry, Fudan University, Shanghai, China ‡ Institute of Biomedical Science, Fudan University, Shanghai, China § Verna and Marrs Mclean Department of Chemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas ¶ Department of Bioengineering, Rice University, Houston, Texas |
| Abstract: | Putative metal-chelate-type ABC transporter HI1470/1 is homologous with vitamin B12 importer BtuCD but exhibits a distinct inward-facing conformation in contrast to the outward-facing conformation of BtuCD. Normal-mode analysis of HI1470/1 reveals the intrinsic asymmetric conformational flexibility in this transporter and demonstrates that the transition from the inward-facing to the outward-facing conformation is realized through the asymmetric motion of individual subunits of the transporter. This analysis suggests that the asymmetric arrangement of the BtuC dimer in the crystal structure of the BtuCD-F complex represents an intermediate state relating HI1470/1 and BtuCD. Furthermore, a twisting motion between transmembrane domains and nucleotide-binding domains encoded in the lowest-frequency normal mode of this type of importer is found to contribute to the conformational transitions during the whole cycle of substrate transportation. A more complete translocation mechanism of the BtuCD type importer is proposed. |
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