cDNA cloning and mitochondrial import of the β-subunit of the human electron-transfer flavoprotein

G. Finocchiaro, I. Colombo, B. Garavaglia, C. Gellera, G. Valdameri, N. Garbuglio, S. Didonato

Research output: Contribution to journalArticlepeer-review


We have isolated a cDNA clone which encodes the entire β-subunit of human electron-transferring flavoprotein (ETF) by screening an expression library from human liver using polyclonal antibodies against porcine ETF. This cDNA encodes a protein of 255 amino-acid residues with a predicted molecular mass of 27877 Da which shows a high degree of similarity with partial amino-acid sequences obtained from both rat liver and Paracoccus denitrificans β-ETF. Northern-blot analysis shows that the human β-ETF mRNA is approximately 1 kb in size and is abundant in liver, heart and skeletal muscle. Incubation with intact mitochondria indicates that the cDNA-encoded β-ETF polypeptide contains the information necessary to reach the mitochondrial matrix. These data are in agreement with previous experiments suggesting that β-ETF, unlike the majority of nuclear-encoded mitochondrial matrix proteins, does not have a cleavable leader peptide. Furthermore, when valinomycin is added to the incubation mixture, the import is abolished, thus demonstrating that it is an energy-dependent process. Interestingly, the sequence analysis of β-ETF protein identifies a 2.63% identity with the Fix A gene product of the nitrogen-fixing bacterium Azorhizobium caulinodans.

Original languageEnglish
Pages (from-to)1003-1008
Number of pages6
JournalEuropean Journal of Biochemistry
Issue number3
Publication statusPublished - 1993

ASJC Scopus subject areas

  • Biochemistry


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