Expression and Iron Storage Properties of Recombinant Human Ferritins in Escherichia Coli: Relevance for Functional Ferritins in Food Systems

Abstract

Ferritin is an iron storage protein found in most living organisms. Human heavy chain (H-) and light chain (L-) ferritin were amplified from human heart cDNA library. Each ferritin gene was inserted down stream of the T7 promoter of bacterial expression, and finally four types of H-, L-, and co-expression vectors were constructed. Recombinant human ferritins were overexpressed and identified with SDS-PAGE and western blotting. The expression levels of recombinant ferritin proteins ranged about 29–36% of whole cell total protein. From atomic absorption spectrometry (AAS) analysis, the rate of iron uptake for H-ferritin was significantly faster than that for the HL-, LH-, and L‐ferritin, respectively. From AAS analysis, the levels of iron content in cells progressively increased in transformants with 0–30 mM ferric citrate in the media. Among these ferritin transformants, the highest amount of cellular iron was observed with H‐ferritin transformant. The total amounts of iron content in E. coli could be sequentially ranked as H-ferritin > HL-ferritin > LH-ferritin > L-ferritin > negative transformants. Expressed recombinant human ferritins indicated that their assembled subunits were able to store iron in the cells. The results of this study further enhances our understanding of iron uptake properties in vivo and suggest similar strategies for using food-grade ferritins for functional foods or iron-fortified food ingredients.

Key Words:

• co-expression
• human ferritin
• iron
• atomic absorption spectrometry

ACKNOWLEDGEMENTS

The author wishes to thank professor Robert E. Levin (University of Massachusetts, Department of Food Science), who reviewed this manuscript.