TCDB is operated by the Saier Lab Bioinformatics Group

1.B.28 The Plastid Outer Envelope Porin of 24 kDa (OEP24) Family

OEP24 is a high conductance, homooligomeric porin in the outer envelopes of pea chloroplasts, etioplasts and non-green root plastids. It forms a voltage-dependent, high conductance, slightly cationic-selective ion channel in reconstituted proteoliposomes. OEP24 transports triosephosphates, dicarboxylates, positively and negatively charged amino acids, sugars, ATP, and inorganic phosphate and thus exhibits low solute specificity. Structural predictions suggest the presence of seven amphipathic β-strands in a β-barrel arrangement. It contains 213 aas and shows a single homologue in Arabidopsis thaliana (212 aas; 60% identity). OEP24 can functionally replace mitochondrial VDAC (MPP family; TC #1.B.28) when the OEP24 gene is expressed in Saccharomyces cerevisiae. Thus, in yeast, it is targeted to the outer mitochondrial membrane, inserts properly, and functionally replaces VDAC. Nevertheless, it shows no sequence similarity to VDAC.

The generalized reaction catalyzed by OEP24 is:

solute (cytoplasm)solute (chloroplast intermembrane space)

References associated with 1.B.28 family:

Bölter, B. and J. Soll. (2001). Ion channels in the outer membranes of chloroplasts and mitochondria: open doors or regulated gates? EMBO J. 20: 1-6. 11230117
Pohlmeyer, K., J. Soll, R. Grimm, K. Hill, and R. Wagner. (1998). A high-conductance solute channel in the chloroplastic outer envelope from Pea. Plant Cell 10: 1207-1216. 9668138
Röhl T., M. Mitzkus and J. Soll. (1999). The outer envelope protein OEP24 from pea chloroplasts can functionally replace the mitochondrial VDAC in yeast. FEBS Lett. 460: 591-594.