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. 2018 Sep 14;38(19):e00306-18. doi: 10.1128/MCB.00306-18

FIG 5.

FIG 5

Model for RACK1:PKCβII phosphorylation of eIF4G(S1093) and its role in controlling dynamic eIF4G:eIF3 assembly. (A) Top panel, eIF4G fragments bearing eIF4E (gold), eIF4A (red), and eIF3 (blue) binding sites; sequences constituting a putative 4-stranded β-sheet are indicated by black stripes. Bottom, fragment 454-1133 contains the intact 4-stranded β-sheet; in unstimulated cells 593-KYEYK-597 anchors an antiparallel β-hairpin with the eIF4E-binding domain. This β-hairpin in the N-terminal unstructured region stabilizes a more complex β-sheet structure including an antiparallel β-hairpin forming in the IDL. The 4-stranded β-sheet may lock the eIF4G configuration and prevent binding to the 43S preinitiation complex. (B) The 609-1133 eIF4G fragment lacks the core inhibitory 593-KYEYK-597 pentapeptide. The 4-stranded β-sheet cannot form, allowing eIF4E/eIF3 assembly, mimicking TPA-stimulated conditions. In this tight complex, during TPA stimulation, activated PKCβII phosphorylates eIF4G(S1093). (C) Phosphorylated 1091-RLpSWG-1095 favors a stable antiparallel β-hairpin with 1017-HIKVQ-1021 in the eIF3c/d-binding site, thus facilitating dissociation of eIF4G from the initiation complex.