IQ (isoleucine-glutamine) motif containing G (IQCG)
IQCG, also called dynein regulatory complex protein 9 (DRC9), belongs to the IQ motif-containing protein family which contains a C-terminal conserved IQ (isoleucine-glutamine) motif and a coiled-coil domain. The IQ motif ([ILV]QxxxRxxxx[RK]), where x stands for any amino-acid residue, interacts with calmodulin (CaM) in a calcium-independent manner and is present in proteins with a wide diversity of biological functions. The expression of IQCG is reduced in the sperm of human asthenospermia patients whose sperm have reduced mobility. It has also been shown to have a role in the calmodulin-mediated calcium signaling pathway in zebrafish haematopoietic development. The human IQCG gene was first reported to be involved in chromosome translocation in a case of acute lymphoid/myeloid leukemia. It expresses predominantly at mice testis during spermatogenesis which interacts with calmodulin in a calcium-dependent manner in the mouse testis. IQCG knockout mice are sterile due to the total immobility of their spermatozoa.
Jiyao W et al.(2023). "The conserved domain database in 2023.",