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Biotin Attachment Domain-Containing Proteins Irreversibly Inhibit Acetyl CoA Carboxylase.

Research paper by Jantana J Keereetaweep, Hui H Liu, Zhiyang Z Zhai, John J Shanklin

Indexed on: 08 Apr '18Published on: 08 Apr '18Published in: Plant physiology



Abstract

The first committed step in fatty acid synthesis is mediated by Acetyl-CoA carboxylase (ACCase), a biotin-dependent enzyme that carboxylates acetyl-CoA to produce malonyl-CoA. ACCase can be feedback-regulated by short-term or long-term exposure to fatty acids in the form of Tween80 (predominantly containing oleic acid; 18:1), which results in reversible or irreversible ACCase inhibition, respectively. Biotin-Attachment-Domain-Containing (BADC) proteins are inactive analogs of biotin carboxyl transfer proteins that lack biotin and their incorporation into ACCase downregulates its activity by displacing active (biotin-containing) biotin carboxyl transferase protein subunits. Arabidopsis thaliana lines containing T-DNA insertions in BADC1, BADC2, and BADC3 were used to generate badc1 badc2 and badc1 badc3 double mutants. The badc1 badc3 mutant exhibited normal growth and development; however, ACCase activity was 26% higher in badc1 badc3 and its seeds contained 30.1% more fatty acids and 32.6% more triacylgycerol TAG, relative to wild-type plants. To assess whether BADC contributes to the irreversible phase of ACCase inhibition, cell suspension cultures were generated from the leaves of badc1 badc3 and wild-type plants and treated with 10 mM Tween80. Reversible ACCase inhibition was similar in badc1 badc3 and wild-type cultures after two days of Tween80 treatment, but irreversible inhibition was reduced by 50% in badc1 badc3 relative to wild-type plants following four days of Tween80 treatment. In this study, we present evidence for two important homeostatic roles for BADC proteins in downregulating ACCase activity: by acting during normal growth and development and by contributing to its long-term irreversible feedback inhibition resulting from oversupply of fatty acids. {copyright, serif} 2018 American Society of Plant Biologists. All rights reserved.