Chloroplast Ubiquitin E3 Ligase SP1: Does It Really Function in Peroxisomes?

Dear Editor, [Pan et al. (2016)][1] presented evidence that the plant ubiquitin E3 ligase SP1 directs proteasome-mediated regulation of the peroxisomal protein import machinery. This was surprising, as SP1 was originally identified as a chloroplast outer envelope-localized regulator of the