Fig. 3. Human ALR can replace the function of yeast Erv1p in the biogenesis of cytosolic Fe/S proteins. (A) Wild-type (WT) and Erv1^ts mutant cells expressing Erv1p, ALR and various ALR fusion proteins were used to analyse the incorporation of ⁵⁵Fe into cytosolic Leu1p by the assay described in Figure 1. Each experiment was performed at least three times. Standard errors are given by bars. (B) Schematic representation of the ALR fusion proteins. The indicated portions of various proteins were fused to the N-terminus of full-length or truncated human ALR (Hofhaus et al., 1999). Localization of the resulting fusion proteins was determined by cell fractionation (cf. Figure 4). Complementation of the growth defect of yeast Erv1^ts cells by the different fusion proteins was assayed by cultivation on rich medium containing glycerol at 37°C for 3 days and was compared with growth of wild-type cells.