The superkiller (SKI) complex is the cytoplasmic co-factor and regulator of the RNA-degrading exosome. In human cells, the SKI complex functions mainly in co-translational surveillance-decay pathways, and its malfunction is linked to a severe congenital disorder, the trichohepatoenteric syndrome. To obtain insights into the molecular mechanisms regulating the human SKI (hSKI) complex, we structurally characterized several of its functional states in the context of 80S ribosomes and substrate RNA. In a prehydrolytic ATP form, the hSKI complex exhibits a closed conformation with an inherent gating system that effectively traps the 80S-bound RNA into the hSKI2 helicase subunit. When active, hSKI switches to an open conformation in which the gating is released and the RNA 3′ end exits the helicase. The emerging picture is that the gatekeeping mechanism and architectural remodeling of hSKI underpin a regulated RNA channeling system that is mechanistically conserved among the cytoplasmic and nuclear helicase-exosome complexes. Display omitted •hSKI has closed and open states connected to different helicase conformations•The intrinsic closed state traps the RNA 3′ end and blocks the RNA exit path•ATP induces the open state of hSKI, allowing 80S ribosome-bound RNA extraction•The hSKI open state primes hSKI2 for channeling RNA to the cytosolic exosome Kögel et al. show that the human SKI complex adopts distinct conformational states to recognize and extract ribosome-bound RNA in a nucleotide-dependent manner. These functional states regulate access of the RNA 3′ end to the cytoplasmic human exosome for co-translational degradation.