This is the C-terminal helix domain found in Eukaryotic translation initiation factor 3 subunit M (eIF3m). In mammalian eIF3a, the C-terminal helix following the PCI domain is involved in interactions with other core subunits [1].

1: Structure of mammalian eIF3 in the context of the 43S preinitiation complex. des Georges A, Dhote V, Kuhn L, Hellen CU, Pestova TV, Frank J, Hashem Y; Nature. 2015;525:491-495. PMID:26344199