Regulates the affinity of calmodulin for calcium. Involved in synaptic plasticity and spatial learning. Interacts with apo-calmodulin; this interaction decreases the affinity of calmodulin for calcium ions. Restricted to dendritic spines of a subset of neurons. Neurogranin is intrinsically unstructured; however, upon binding with CaM, The IQ domain adopts a helical conformation. Disulfide bond formation is redox-sensitive. The cysteine residues are readily oxidized by several nitric acid (NO) donors and other oxidants to form intramolecular disulfide. Cys-51 can form a disulfide with any other of the cysteine residues with an order of reactivity Cys-9 > Cys-4 > Cys-3 (By similarity). Phosphorylated at Ser-36 by PHK and PKC, phosphorylation prevents interaction with Calmodulin and interrupts several learning- and memory-associated functions. Belongs to the neurogranin family.