Figure 6: Proposed mechanism of IQCG in calcium/CaM signalling.

The cytoplasmic Ca²⁺ level is low in resting cells and IQCG binds Ca²⁺-free CaM via the IQ motif (left panel). When specific signals trigger an increase of the cytoplasmic Ca²⁺ level, the affinity between CaM and IQ motif decreases. As IQCG and CaMKIV are hypothetically bound by putatively scaffold proteins including HSP70 and other unknown molecules in the complex (a big circle of question mark depicted with dotted line), both lobes of CaM may subsequently bind CaMKIV (indicated by solid line) instead of reassociating to the new sites of IQCG (indicated by dotted line; middle panel). The binding of CaM activates CaMKIV and its downstream pathway, and promotes cell proliferation (right panel).