The Arabidopsis ABC transporter COMATOSE (CTS; AtABCD1) is required for uptake into the peroxisome of a wide range of substrates for beta-oxidation, but it is uncertain whether CTS itself is the transporter or if the transported substrates are free acids or CoA esters. To establish a system for its biochemical analysis, CTS was expressed in Saccharomyces cerevisiae. The plant protein was correctly targeted to yeast peroxisomes, was assembled into the membrane with its nucleotide binding domains in the cytosol and exhibited basal ATPase activity that was sensitive to aluminium fluoride and abrogated by mutation of a conserved Walker A motif lysine residue. The yeast pxa1 pxa2Delta mutant lacks the homologous peroxisomal ABC transporter and is unable to grow on oleic acid. Consistent with its exhibiting a function in yeast akin to that in the plant, CTS rescued the oleate growth phenotype of the pxa1 pxa2Delta mutant, and restored beta-oxidation of fatty acids with a range of chain lengths and varying degrees of desaturation. Interestingly, when expressed in yeast peroxisomal membranes, the basal ATPase activity of CTS could be stimulated by fatty acyl CoAs but not by fatty acids. The implications of these findings for the function and substrate specificity of CTS are discussed.
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|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
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