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Isolation and characterization of a cDNA clone for human ferritin heavy chain
Insights
Researchers isolated a human ferritin heavy (H) chain cDNA clone using synthetic probes. This confirms the cloned DNA codes for the H subunit, suggesting a complex gene structure for ferritin H chains.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Ferritin is the primary intracellular iron-storage protein.
- It comprises heavy (H) and light (L) subunits, with distinct molecular weights.
- Understanding subunit composition is crucial for iron metabolism research.
Purpose of the Study:
- To isolate and characterize the cDNA clone for human ferritin heavy (H) chains.
- To confirm the identity of the cloned DNA sequence.
- To investigate the genetic basis of ferritin H chain expression.
Main Methods:
- Screening of a human lymphocyte cDNA library using synthetic oligodeoxyribonucleotides.
- Hybridization assays to confirm clone specificity for H-chain mRNA.
- Amino acid sequence analysis of the cloned DNA.
- Genomic analysis to study gene structure.
Main Results:
- A cDNA clone for human ferritin H chains was successfully isolated.
- The clone specifically hybridized to H-chain mRNA, confirming its identity.
- The deduced amino acid sequence closely matched a minor component in human spleen ferritin.
- Genomic analysis indicated that H chains may be encoded by a multigene family or possess numerous exons.
Conclusions:
- The isolated cDNA clone definitively codes for the human ferritin H subunit.
- The minor component in spleen ferritin is identified as the H subunit.
- Ferritin H chain genes likely represent a multigene family or have complex exon structures.
Abstract:
Ferritin, the main iron-storage protein, is composed of two partially homologous subunits, heavy (H) and light (L), with MrS of 21,000 and 19,000, respectively. We have isolated a cDNA clone for human ferritin H chains by screening a human lymphocyte cDNA library with synthetic oligodeoxyribonucleotides. The oligonucleotide sequences were derived from two pentapeptides found in human spleen ferritin. The selected clone hybridized to both probes and selected H-chain mRNA, but not L-chain mRNA, when hybridized to HeLa cell mRNA. These results indicate that the cloned DNA codes for a H chain of human ferritin. Since the amino acid sequence derived from the cloned DNA was almost identical to the partial amino acid sequence of a minor component found in human spleen ferritin, we conclude that the minor sequence found in human spleen ferritin must be a H subunit. Genomic analysis gives a complex pattern that suggests that ferritin H chains are encoded by a multigene family or have an unusually large number of exons.