Fatty acid biosynthesis in mitochondria of grasses: malonyl-coenzyme A is generated by a mitochondrial-localized acetyl-coenzyme A carboxylase.
We present biochemical evidence for the occurrence of a 250-kD multifunctional acetyl-coenzyme A carboxylase in barley (Hordeum vulgare) mitochondria. Organelles from 6-d-old barley seedlings were purified by differential centrifugation and Percoll density gradient centrifugation. Upon analysis by two-dimensional Blue-native (BN)/SDS-PAGE, an abundant 250-kD protein can be visualized, which runs at 500 kD on the native gel dimension. A similar 500-kD complex is present in etioplasts from barley. The mitochondrial 250-kD protein is biotinylated as indicated by specific reaction with an antibody directed against biotin. Peptide sequence analysis by electrospray ionization tandem mass spectrometry of the 250-kD proteins from both organellar fractions revealed amino acid sequences that are 100% identical to plastidic acetyl-coenzyme A carboxylase from wheat (Triticum aestivum). The 500-kD complex was also detected in wheat mitochondria, but is absent in mitochondrial fractions from Arabidopsis. Specific acetyl-coenzyme A carboxylation activity in barley mitochondria is higher than in etioplasts, suggesting an important role of mitochondria in fatty acid biosynthesis. Functional implications are discussed.
Focke
Manfred
M
Botanik II, Universität Karlsruhe, 76128 Karlsruhe, Germany.
Gieringer
Ellen
E
Schwan
Sabine
S
Jänsch
Lothar
L
Binder
Stefan
S
Braun
Hans-Peter
HP
D000103:Acetyl-CoA Carboxylase / Q000737:chemistry / Q000378:metabolism*; D000595:Amino Acid Sequence; D005227:Fatty Acids / Q000096:biosynthesis*; D001467:Hordeum / Q000201:enzymology; D008316:Malonyl Coenzyme A / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D006109:Poaceae / Q000201:enzymology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013820:Thermolysin; D014908:Triticum / Q000201:enzymology
D005227:Fatty Acids; D010446:Peptide Fragments; D008316:Malonyl Coenzyme A; D013820:Thermolysin; D000103:Acetyl-CoA Carboxylase