= ADP-ribosylation
{c}
<ADP-ribosylation> transfers an ADP-ribose group from <NAD+> to a target, commonly a <protein>, with release of <nicotinamide>. It is a <post-translational modification> distinct from <phosphorylation>: the transferred chemical group is different, as are the <enzymes> that add or remove it. A modification can alter a target's activity or interactions without changing its encoded <protein sequence>. <ADP-ribosylation of membrane proteins catalyzed by cholera toxin: basis of the activation of adenylate cyclase by D. M. Gill and others>[1978, abstract and pp. 3050–3054: toxin-dependent protein modification and adenylate-cyclase activity]{ref}
The <cholera toxin> experiments linked <NAD+>-dependent modification of a membrane-associated <protein> to persistent activation of <adenylyl cyclase>. They provide a concrete example of how a covalent chemical change can amplify a cellular signal. Other ADP-ribosylation systems have different targets and outcomes, so the chemical name alone does not specify one biological response.
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