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LTP can be induced by artificially injecting Ca MKII.
When Ca MKII is infused in postsynaptically in the hippocampal slices and intracellular perfusion or viral expression, there is a two- to threefold increase in the response of the synapse to glutamate and other chemical signals.
The isoforms derive from the alpha, beta, gamma, and delta genes.
All of the isoforms of Ca MKII have: a catalytic domain, an autoinhibitory domain, a variable segment, and a self-association domain.
The autoinhibitory domain features a pseudosubstrate site, which binds to the catalytic domain and blocks its ability to phosphorylate proteins.
The structural feature that governs this autoinhibition is the Threonine 286 residue.
The sensitivity of the Ca MKII enzyme to calcium and calmodulin is governed by the variable and self-associative domains.
This sensitivity level of Ca MKII will also modulate the different states of activation for the enzyme.
Phosphorylation of the Threonine 286 site allows for the activation of the catalytic domain.
However, the Threonine 286 residue eventually becomes dephosphorylated, leading to inactivation of Ca MKII.
Autophosphorylation is the process in which a kinase attaches a phosphate group to itself.
Autophosphorylation is enhanced by the structure of the holoenzyme because it is present in two stacked rings.
The close proximity of these adjacent rings increases the probability of phosphorylation of neighboring Ca MKII enzymes, furthering autophosphorylation.
Initially, the enzyme is activated; however, autophosphorylation does not occur because there is not enough Calcium or calmodulin present to bind to neighboring subunits.