ATP-binding RNA helicase involved in translation initiation. Part of the 43S preinitiation complex that is required for efficient initiation on mammalian mRNAs with structured 5'- UTRs by promoting efficient NTPase-dependent 48S complex formation. Specifically binds to the 40S ribosome near the mRNA entrance. Does not possess a processive helicase activity. {ECO:0000269|PubMed:19109895; ECO:0000269|PubMed:23706745}.