The OXA2a Insertase of Arabidopsis Is Required for Cytochrome c Maturation. Issue 2 (5th August 2020)

• Record Type: Journal Article
• Authors: Kolli, Renuka; Engstler, Carina; Akbaş, Şebnem; Mower, Jeffrey P.; Soll, Jürgen; Carrie, Chris
• Is Part Of: Plant physiology. Volume 184:Issue 2(2020)
• Page Start: 1042
• Page End: 1055
• Publication Date: 2020-08-05
• Subjects: Plant physiology -- Periodicals; Botany -- Periodicals; Periodicals; Electronic journals; 571.2
• DOI: 10.1104/pp.19.01248
• Languages: English
• ISSNs: 0032-0889

Abstract

Abstract : Arabidopsis mitochondria require a specific inner membrane insertase for efficient biogenesis of c-type cytochromes. Abstract: In yeast ( Saccharomyces cerevisiae ) and human ( Homo sapiens ) mitochondria, Oxidase assembly protein1 (Oxa1) is the general insertase for protein insertion from the matrix side into the inner membrane while Cytochrome c oxidase assembly protein18 (Cox18/Oxa2) is specifically involved in the topogenesis of the complex IV subunit, Cox2. Arabidopsis ( Arabidopsis thaliana ) mitochondria contain four OXA homologs: OXA1a, OXA1b, OXA2a, and OXA2b. OXA2a and OXA2b are unique members of the Oxa1 superfamily, in that they possess a tetratricopeptide repeat (TPR) domain at their C termini. Here, we determined the role of OXA2a by studying viable mutant plants generated by partial complementation of homozygous lethal OXA2a transfer-DNA insertional mutants using the developmentally regulated ABSCISIC ACID INSENSITIVE3 ( ABI3 ) promoter. The ABI3p:OXA2a plants displayed growth retardation due to a reduction in the steady-state abundances of both c -type cytochromes, cytochrome c 1 and cytochrome c . The observed reduction in the steady-state abundance of complex III could be attributed to cytochrome c 1 being one of its subunits. Expression of a soluble heme lyase from an organism with cytochrome c maturation system III could functionally complement the lack of OXA2a. This implies that OXA2a is required for the system I cytochrome c maturation of Arabidopsis. Due to the interaction of OXA2a with Cytochrome c maturation protein CcmF C-terminal-like protein (CCMFC ) in a yeast split-ubiquitin based interaction assay, we propose that OXA2a aids in the membrane insertion of CCMFC, which is presumed to form the heme lyase component of the cytochrome c maturation pathway. In contrast with the crucial role played by the TPR domain of OXA2b, the TPR domain of OXA2a is not essential for its functionality.