- P-ISSN 1225-0163
- E-ISSN 2288-8985
IQ motif-containing GTPase-activating proteins (IQGAPs), which are well-known Ca2+-independent calmodulin (CaM) binding proteins, are involved in various cellular functions such as cell proliferation, carcinogenesis and cell migration. The IQGAP3 similar to IQGAP1 has four repeated IQ motifs, which are crucial for CaM binding. It has been recently shown that all four IQ motifs of the IQGAP1 could bind to CaM, while not clear the binding of four IQ motifs of the IQGAP3. In this study, we examined the binding between CaM and each IQ motif of IQGAP3. As a result, we found that IQ2 and IQ3, but not IQ1 and IQ4, have a Ca2+-independent CaM binding activity. We also found that IQ(3.5-4.4) on the IQGAP3 has Ca2+-dependent CaM binding activity as similar with that of IQGAP1. This finding indicates that IQ motifs of the IQGAP3 plays a dynamic role via different interaction of IQ motifs with Ca2+/CaM or apoCaM.
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