Zinc-Ligand Swapping Mediated Complex Formation and Sulfur Transfer between SufS and SufU for Iron–Sulfur Cluster Biogenesis in Bacillus subtilis† Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, Shimo-ohkubo 255, Sakura-ku, Saitama 338-8570, Japan‡ Department of Bioscience, Graduate School of Agriculture, Tokyo University of Agriculture, Sakuragaoka 1-1-1, Setagaya-ku, Tokyo 156-8502, JapanJ. Am. Chem.