Direct evidence for expression of type II flavoprotein subunit in human complex II (succinate-ubiquinone reductase).
Succinate-ubiquinone reductase (complex II) is an important enzyme complex in aerobic respiration and the tricarboxylic acid cycle. We recently identified two distinct cDNAs for the human flavoprotein subunit (Fp) from a single individual and demonstrated mRNAs of these two isoforms, Type I Fp and Type II Fp, in skeletal muscle, liver, brain, heart, and kidney. Type I Fp was expressed at higher levels than Type II Fp in all cases. In the present study, the biochemical properties of Type II Fp-containing complex II in Raji cells predominantly expressing Type II Fp were investigated. Complex II having Type II Fp was separated from that having Type I Fp by isoelectric focusing in the presence of sucrose monolaurate. Together with the fact that succinate-ubiquinone reductase activity of mitochondria prepared from Raji cell was almost identical to that from human liver, these results clearly indicate the presence of two distinct isoforms of active complex II in human mitochondria.
Tomitsuka
Eriko
E
Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113 0033, Japan.
Goto
Yu-ichi
Y
Taniwaki
Masafumi
M
Kita
Kiyoshi
K
D000595:Amino Acid Sequence; D015139:Blotting, Southern; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D042963:Electron Transport Complex II / Q000737:chemistry*; D015180:Electrophoresis, Gel, Two-Dimensional; D004591:Electrophoresis, Polyacrylamide Gel; D005420:Flavoproteins / Q000737:chemistry*; D006801:Humans; D020128:Inhibitory Concentration 50; D007525:Isoelectric Focusing; D008099:Liver / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution
D018076:DNA, Complementary; D005420:Flavoproteins; D020033:Protein Isoforms; D012313:RNA; D042963:Electron Transport Complex II