This work was supported by start-up funds from the Life Sciences Institute and the College of Pharmacy at the University of Michigan as well as by the Vahlteich Research Award Fund, College of Pharmacy at the University of Michigan (to SGT). This work was also supported by the Ministerio de Ciencia e Innovacion (MICINN) (to FL). ASAM was supported by a Huygens Scholarship Programme for International Students as well as the Utrecht Scholarship for Pharmaceutical Sciences (Netherlands). MASM was supported by the FICYT Asturias. We thank Prof. David Sherman (University of Michigan) for the generous gift of CurB and JamF proteins as well as AsbC and AsbD plasmids. Vanessa R. Porter is acknowledged for her help with generating the figures for determination of kinetic parameters. We acknowledge Jessica M. Pero for initial TioO, TioP, and TioQ cloning experiments. We thank Dr. Anita Sheoran for initial TioS(T<INF>4</INF>) characterization by TCA precipitation assays.