InterPro domain: IPR000048

The IQ motif is an extremely basic unit of about 23 amino acids, whose conserved core usually fits the consensus A-x(3)-I-Q-x(2)-F-R-x(4)-K-K. The IQ motif, which can be present in one or more copies, serves as a binding site for different EF-hand proteins including the essential and regulatory myosin light chains, calmodulin (CaM), and CaM-like proteins [ 1 , 2 ].Many IQ motifs are protein kinase C (PKC) phosphorylation sites [ 3 , 4 ].

Resolution of the 3D structure of scallop myosin has shown that the IQ motif forms a basic amphipathic helix [ 5 ].

Some proteins known to contain an IQ motif are listed below:

• A number of conventional and unconventional myosins.
• Neuromodulin (GAP-43). This protein is associated with nerve growth. It is a major component of the motile "growth cones" that form the tips of elongating axons.
• Neurogranin (NG/p17). Acts as a "third messenger" substrate of protein kinase C-mediated molecular cascades during synaptic development and remodeling.
• Sperm surface protein Sp17.
• Ras GTPase-activating-like protein IQGAP1. IQGAP1 contains 4 IQ motifs.

This entry covers the entire IQ motif.

1. Unconventional myosins. Curr. Opin. Cell Biol. 4, 27-35
2. Sequence motifs for calmodulin recognition. FASEB J. 11, 331-40
3. Purification and characterization of a brain-specific protein kinase C substrate, neurogranin (p17). Identification of a consensus amino acid sequence between neurogranin and neuromodulin (GAP43) that corresponds to the protein kinase C phosphorylation site and the calmodulin-binding domain. J. Biol. Chem. 266, 229-37
4. Studies with synthetic peptide substrates derived from the neuronal protein neurogranin reveal structural determinants of potency and selectivity for protein kinase C. Biochemistry 32, 1032-9
5. Structure of the regulatory domain of scallop myosin at 2.8 A resolution. Nature 368, 306-12