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IQ (isoleucine-glutamine) motif containing G and D (IQCG and IQCD) IQCG and IQCD belong to the IQ motif-containing protein family which contain a C-terminal conserved IQ (isoleucine-glutamine) motif and a coiled-coil domain. The IQCG protein (also known as DRC9 and CFAP122) is essential for sperm flagellum formation in mice. The IQCD protein (also known as DRC10) is involved in sperm fertilization and the acrosome reaction. Both proteins are components of the nexin-dynein regulatory complex (N-DRC), a key regulator of ciliary/flagellar motility. IQCG and IQCD proteins contain a central coiled-coil domain and a C-terminal IQ (isoleucine-glutamine) motif ([ILV]QxxxRxxxx[RK]), where x stands for any amino-acid residue, that interacts with calmodulin (CaM) in a calcium-independent manner. IQ motif-containing proteins that are known to bind calmodulin (CaM) have a wide diversity of biological functions, and they include neuronal growth proteins, myosins, voltage-operated channels, phosphatases, Ras exchange proteins, sperm surface proteins, Ras Gap-like proteins, spindle-associated proteins, and several proteins in plants. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",