hide
Free keywords:
-
Abstract:
Dear Editor,Mitochondria act as cellular hubs of energy transformation and metabolite conversion in most eukaryotes. Plant mitochondrial electron transport chains are particularly flexible, featuring components that can bypass proton translocation steps, such as ALTERNATIVE NAD(P)H DEHYDROGENASES and ALTERNATIVE OXIDASES (AOXs). PLANT UNCOUPLING MITOCHONDRIAL PROTEINS (PUMPs or plant UNCOUPLING PROTEINS [UCPs]) have been identified in plants as homologs of mammalian UCPs, and their physiological roles have been investigated in the context of mitochondrial energy metabolism. To dissect UCP function in Arabidopsis (Arabidopsis thaliana), the 2 most conserved family members, UCP1 and UCP2, have been genetically ablated assuming that they both reside in the inner mitochondrial membrane. Yet, contradicting results have been reported on plant UCP2 localization. After UCP1 (Maia et al. 1998) and UCP2 (Watanabe et al. 1999) were identified as plant homologs of mammalian UCP1, 6 Arabidopsis isogenes were named PUMP1 to PUMP6 (Borecký et al. 2006). However, PUMP4 to PUMP6 exhibit properties typical of the phylogenetically related mitochondrial dicarboxylate carrier (DIC) proteins (Palmieri et al. 2008). Accordingly, PUMPs were regrouped into plant UCP1 to UCP3 and plant DIC1 to DIC3 (Supplemental Fig. S1) (Palmieri et al. 2008). UCP1 and UCP2 are highly similar in sequence and share 72% amino acid identity (Supplemental Fig. S2A) (Monné et al. 2018). We provide evidence that UCP2 localizes to the Golgi unlike UCP1, which localizes to the mitochondria, and we provide perspectives on UCP protein function, Golgi membrane transport, and subcellular targeting principles of membrane proteins.
