Expression and structural and functional properties of human ferritin L-chain from Escherichia coli.
The human ferritin L-chain cDNA was cloned into a vector for overproduction in Escherichia coli, under the regulation of a lambda promoter. The plasmid obtained contains the full L-chain coding region modified at the first two codons. It is able to direct the synthesis of the L-chain which can constitute up to 15% of the total soluble protein of bacterial extract. The L-chains assemble to form a ferritin homopolymer with electrophoretic mobility, molecular weight, thermal stability, spectroscopic, and immunological properties analogous to natural ferritin from human liver (95% L-chain). This recombinant L-ferritin is able to incorporate and retain iron in solution at physiological pH values. At variance with the H-ferritin, the L form does not uptake iron at acidic pH values and does not show detectable ferroxidase activity. It is concluded that ferritin L-chain lacks the ferroxidase site present in the H-chain and that the two chains may have specialized functions in intracellular iron metabolism.
Levi
S
S
Department of Biomedical Sciences and Technology, University of Milan, Ospedale San Raffaele, Milano, Italy.
Salfeld
J
J
Franceschinelli
F
F
Cozzi
A
A
Dorner
M H
MH
Arosio
P
P
D015153:Blotting, Western; D002570:Ceruloplasmin / Q000378:metabolism; D003062:Codon; D004247:DNA / Q000032:analysis; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics*; D005293:Ferritins / Q000096:biosynthesis* / Q000235:genetics / Q000302:isolation & purification; D005822:Genetic Vectors; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000032:analysis; D007525:Isoelectric Focusing; D010957:Plasmids; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000096:biosynthesis* / Q000302:isolation & purification; D013329:Structure-Activity Relationship
D003062:Codon; D011994:Recombinant Proteins; D004247:DNA; D005293:Ferritins; D007501:Iron; D002570:Ceruloplasmin