Regulates the affinity of calmodulin for calcium. Involved in synaptic plasticity and spatial learning (By similarity). Interacts with apo-calmodulin; this interaction decreases the affinity of calmodulin for calcium ions. Restricted to dendritic spines of a subset of neurons. Highly enriched in brain with restricted expression in neuronal subsets primarily in the cortex, striatum, and hippocampus as well as certain nuclei within the thalamus, hypothalamus and olfactory bulb. Accumulates postsynaptically in dendritic spines of neostriatal neurons. Neurogranin is intrinsically unstructured; however, upon binding with CaM, The IQ domain adopts a helical conformation. Phosphorylated at Ser-36 by PHK and PKC. Phosphorylation prevents interaction with Calmodulin and interrupts several learning- and memory-associated functions (By similarity). Phosphorylation is activated by calcium, phospholipids, and diacylglycerol. Phosphorylation inhibits binding to calmodulin both in the presence and absence of calcium. 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. Belongs to the neurogranin family.