Journal Article

Microsomal Electron Transfer in Higher Plants: Cloning and Heterologous Expression of NADH-Cytochrome b sub(5) Reductase from Arabidopsis

Kusumi, T, Tanaka, Y, Fukuchi-Mizutani, M, Ohta, D, Mizutani, M

1999

Overview

AtCBR, a cDNA encoding NADH-cytochrome (Cyt) b sub(5) reductase, and AtB5-A and AtB5-B, two cDNAs encoding Cyt b sub(5), were isolated from Arabidopsis. The primary structure deduced from the AtCBR cDNA was 40% identical to those of the NADH-Cyt b sub(5) reductases of yeast and mammals. A recombinant AtCBR protein prepared using a baculovirus system exhibited typical spectral properties of NADH-Cyt b sub(5) reductase and was used to study its electron-transfer activity. The recombinant NADH-Cyt b sub(5) reductase was functionally active and displayed strict specificity to NADH for the reduction of a recombinant Cyt b sub(5) (AtB5-A), whereas no Cyt b sub(5) reduction was observed when NADPH was used as the electron donor. Conversely, a recombinant NADPH-Cyt P450 reductase of Arabidopsis was able to reduce Cyt b sub(5) with NADPH but not with NADH. To our knowledge, this is the first evidence in higher plants that both NADH-Cyt b sub(5) reductase and NADPH-Cyt P450 reductase can reduce Cyt b sub(5) and have clear specificities in terms of the electron donor, NADH or NADPH, respectively. This substrate specificity of the two reductases is discussed in relation to the NADH- and NADPH- dependent activities of microsomal fatty acid desaturases.

• Subject: Arabidopsis thaliana