1.B.77 The Chloroplast Outer Membrane Porin (Oep23) Family
Oep23 is found in the entire plant lineage from green algae to flowering plants. It is expressed in all organs and developmental states tested so far. The reconstituted recombinant protein Oep23 from pea forms a high conductance ion channel with a maximal conductance in the fully open state of 466 ± 14pS at a holding potential of +100 mV (in 250 mM KCl) (Goetze et al. 2015). The Oep23 channel is cation-selective (PK+ : PCl- = 15 : 1) with a voltage-dependent open probability of maximal Vmem = 0 mV. Oep23 activity appears to be a single channel unit that does not assemble into a multiple pore complex like bacterial type porins or mitochondrial voltage dependent anion channels. Thus, Oep23s are ion channels in the outer envelope of chloroplasts involved in solute exchange (Goetze et al. 2015)
The generalized reaction catalyzed by Oep23 is:
solutes (out) ↔ soutes (in)
References:
The chloroplast outer membrane ion channel-forming porin of 207 aas and 9 predcted transmembrane β-strands, Oep23. A member of the DUF1990 Superfamily; found in chloroplast outer membranes from simple algae to higher plants (Goetze et al. 2015).
Plants
Oep23 of Medicago truncatula (Barrel medic) (Medicago tribuloides)
Uncharacterized protein with 9 N-terminal TMSs, homologous to members of the YndJ Family (9.B.227) and a C-terminal domain with extensive sequence similarity to members of the Oep23 family.
UP of Cellulomonas fimi
Bacterial Oep23 homologue of 219 aas.
Planctomycetes
Oep23 homologue of Rhodopirellula baltica
Oep23 homologue of 234 aas
Amoebozoa
Oep23 homologue of Acanthamoeba castellanii
Oep23 homologue of 255 aas
Plants (Algae)
Oep23 homologue of Chlorella variabilis (Green alga)
Oep23 homologue of 197 aas
Acidobacteria
Oep23 homologue of 196 aas
Actinobacteria
Oep23 homologue of Kitasatospora setae (Streptomyces setae)
Putative glycogen metabolism protein of 197 aas
Actinobacteria
Oep23 homologue of Leifsonia rubra
Oep23 homologue of 198 aas
Deinococcus/Thermus
Oep23 homologue of Deinococcus radiodurans
Oep23 of 242 aas
Oep23 of Chondrus crispus (Carrageen Irish moss) (Polymorpha crispa)
Oep23 homologue of 279 aas (DUF1990 superfamily).
Stramenopiles
Oep23 homologue of Thalassiosira oceanica (Marine diatom)
Oep23 homologue of 362 aas
Stramenopiles
Oep23 homologue of Phaeodactylum tricornutum
Oep23 homologue of 238 aas
Haptophyceaea
Oep23 homologue of Emiliania huxleyi
Oep23 homologue of 333 aas
Stramenopiles
Oep23 homologue of Nannochloropsis gaditana