Figure 1.

PCBP1 delivers iron to ferritin in Saccharomyces cerevisiae. (A) Activation of an iron-regulated, Aft1-responsive promoter (FeRE) fused to the HIS3 coding sequence when cytosolic iron is transferred into ferritin. (B) PCBP1-dependent activation of the FeRE/HIS3 reporter in yeast expressing ferritin, but not in yeast without ferritin. Transformed strains were plated in serial dilutions on media with and without histidine. (C and D) PCBP1 increases ferritin mineralization. Strains transformed as in B were grown with ⁵⁵FeCl₃, ferritin was isolated by native gel electrophoresis and iron within ferritin was detected by autoradiography. In D, replicates were normalized to the vector transformed strain (n=5). (E) PCBP1 did not affect ferritin protein levels (n=10). (F) PCBP1-dependent increase in surface ferric reductase activity in yeast expressing ferritin, but not in yeast without ferritin (n=5). *P<0.002. This and subsequent p values were determined using 2-tailed t test.