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. 2020 Jan 25;9(2):152. doi: 10.3390/plants9020152

Figure 6.

Figure 6

Model for negative autoregulation of psbA translation initiation in the context of the HCF244/OHP1/OHP2 complex. OHP1 and OHP2 are integral thylakoid proteins, and HCF244 is tethered to OHP2 on the stromal face of the membrane [13,14,16,17]. HCF173 binds the 5′-UTR of psbA mRNA and is required for psbA translation initiation [23,32,34]. We propose that stroma-exposed features of the complex (HCF244 and/or OHP2’s stromal tail) collaborate with HCF173 to activate psbA translation initiation, and that the presence of D1 in the complex inhibits communication to HCF173. This is a simplified cartoon that does not incorporate evidence that other PSII core subunits (PsbI, D2, PsbE, PsbF) also associate with the HCF244/Ycf39 complex under some conditions [13,14,17]. Ycf48 (the HCF136 homolog in cyanobacteria) associates with this complex when downstream steps in PSII assembly are disrupted, but there is conflicting evidence about the association of HCF136 with the HCF244 complex in plants [13,14,17].