Component of the intraflagellar transport (IFT) complex B: together with IFT81, forms a tubulin-binding module that specifically mediates transport of tubulin within the cilium. Binds beta-tubulin via its basic region. Required for ciliogenesis (By similarity). Essential for flagellogenesis during spermatogenesis (PubMed:31004481). Component of the IFT complex B, at least composed of IFT20, IFT22, HSPB11/IFT25, IFT27, IFT46, IFT52, TRAF3IP1/IFT54, IFT57, IFT74, IFT80, IFT81, and IFT88 (PubMed:16775004, PubMed:23810713). Interacts with IFT81; the interaction is direct: within the IFT complex B, IFT74 and IFT81 mediate the transport of tubulin within the cilium. Interacts (via basic region) with beta-tubulin (via acidic region); interaction is direct. Interacts with ARL13B and IFT88. Interacts (via the IFT74/IFT81 heterodimer) with RABL2B (By similarity). Interacts with IFT57 and TTC30B (PubMed:23810713). In male germ cells, strongly expressed in the vesicles of spermatocytes and round spermatids and also in the acrosome and centrosome regions of elongating spermatids and in developing sperm tails. Predominantly expressed in testis, but also detected in other organs containing cilia-bearing cells, including lung, brain and kidney (at protein level). In testis, expression starts at day 12 and strongly increases on day 20 and thereafter, temporally correlating with the first wave of spermatogenesis. Belongs to the IFT74 family. Truncated N-terminus.