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HP30‐2, a mitochondrial PRAT protein for import of signal sequence‐less precursor proteins in Arabidopsis thaliana

Rossig, Claudia, Gray, John, Valdes, Oscar, Rustgi, Sachin, von Wettstein, Diter, Reinbothe, Christiane, Reinbothe, Steffen
Journal of integrative plant biology 2017 v.59 no.8 pp. 535-551
Arabidopsis thaliana, amino acid transporters, biogenesis, chloroplasts, electron transport chain, green fluorescent protein, hydrophobicity, mitochondria, protein tagging
Chloroplasts and mitochondria contain a family of putative preprotein and amino acid transporters designated PRAT. Here, we analyzed the role of two previously characterized PRAT protein family members, encoded by At3g49560 (HP30) and At5g24650 (HP30‐2), in planta using a combination of genetic, cell biological and biochemical approaches. Expression studies and green fluorescent protein tagging identified HP30‐2 both in chloroplasts and mitochondria, whereas HP30 was located exclusively in chloroplasts. Biochemical evidence was obtained for an association of mitochondrial HP30‐2 with two distinct protein complexes, one containing the inner membrane translocase TIM22 and the other containing an alternative NAD(P)H dehydrogenase subunit (NDC1) implicated in a respiratory complex 1‐like electron transport chain. Through its association with TIM22, HP30‐2 is involved in the uptake of carrier proteins and other, hydrophobic membrane proteins lacking cleavable NH₂‐terminal presequences, whereas HP30‐2's interaction with NDC1 may permit controlling mitochondrial biogenesis and activity.