Download MendeleyAn Interprotein Co-S Coordination Complex in the B 12 -Trafficking Pathway.
Li, Z., Mascarenhas, R., Twahir, U.T., Kallon, A., Deb, A., Yaw, M., Penner-Hahn, J., Koutmos, M., Warncke, K., Banerjee, R.(2020) J Am Chem Soc 142: 16334-16345
- PubMed: 32871076
- DOI: https://doi.org/10.1021/jacs.0c06590
- Primary Citation of Related Structures:
6X8Z - PubMed Abstract:
The CblC and CblD chaperones are involved in early steps in the cobalamin trafficking pathway. Cobalamin derivatives entering the cytoplasm are converted by CblC to a common cob(II)alamin intermediate via glutathione-dependent alkyltransferase or reductive elimination activities. Cob(II)alamin is subsequently converted to one of two biologically active alkylcobalamins by downstream chaperones. The function of CblD has been elusive although it is known to form a complex with CblC under certain conditions. Here, we report that CblD provides a sulfur ligand to cob(II)alamin bound to CblC, forming an interprotein coordination complex that rapidly oxidizes to thiolato-cob(III)alamin. Cysteine scanning mutagenesis and EPR spectroscopy identified Cys-261 on CblD as the sulfur donor. The unusual interprotein Co-S bond was characterized by X-ray absorption spectroscopy and visualized in the crystal structure of the human CblD thiolato-cob(III)alamin complex. Our study provides insights into how cobalamin coordination chemistry could be utilized for cofactor translocation in the trafficking pathway.
Organizational Affiliation:
Department of Biological Chemistry, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0600, United States.
