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 (PubMed:23990561). Binds beta-tubulin via its basic region (PubMed:23990561). Required for ciliogenesis (PubMed:23990561). Essential for flagellogenesis during spermatogenesis (PubMed:33689014). 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:23990561, PubMed:33531668). Interacts with IFT81; the interaction is direct (PubMed:15955805, PubMed:23990561, PubMed:33531668). Within the IFT complex B, IFT74 and IFT81 mediate the transport of tubulin within the cilium (PubMed:15955805, PubMed:23990561). Interacts (via basic region) with beta-tubulin (via acidic region); interaction is direct (PubMed:23990561). Interacts with ARL13B and IFT88 (PubMed:24339792). Interacts (via the IFT74/IFT81 heterodimer) with RABL2B (PubMed:28428259, PubMed:28625565). Interacts with IFT57 and TTC30B (By similarity). Localizes along primary cilia at interphase and around the basal body/centriole at interphase and mitosis (PubMed:15024030). 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 (By similarity). Highly expressed in adult and fetal kidney and expressed at lower level in adult heart, placenta, lung, liver and pancreas, and in fetal heart, lung and liver. Little to no expression was detected in adult brain and skeletal muscle or in fetal brain, thymus and spleen (PubMed:11683410). Detected in sperm (at protein level) (PubMed:33689014). The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. The disease is caused by variants affecting the gene represented in this entry. A homozygous variant at codon 86 has been identified in 2 unrelated affected individuals. In addition to encoding a missense, this variant also affects splicing, predominantly through the induction of an in-frame deletion of 10 amino acids within exon 3. Other minor transcripts can be detected in patient's sperm that use cryptic donor sites present in intron 3, leading either to the retention of 18 bp of intron 3 and an in-frame insertion of 6 amino acids, or to the retention of 108 bp of intron 3, which induces a frameshift and a truncated protein. Belongs to the IFT74 family. Truncated C-terminus. Truncated N-terminus.