: 149–165  Among other interactions, it forms a transcription complex with Retinoid-related Orphan nuclear-receptor transcription factor α (RORα) following interactions with an activator, Histone acetyltransferase KAT5, sometimes referred to as TIP60, and it is in the signaling mediated by metabotropic glutamate receptor 1 (mGluR1). Resonant Recognition Modeling of the ataxin 1 protein has shown possible binding sites for growth factor independent transcription repressor 1 (Gfi-1). The predictions of this computational model reveal an interaction that could play a role in SCA1 pathology, because the Gfi-1 protein is known to cause selective degradation of Purkinje cells. : 149–165  It is the extensive involvement of ataxin 1 in many different functions that make understanding the biochemical pathophysiology of its mutant form difficult to identify and understand. : 15 The mechanism by which expanded CAG repeat regions in ataxin 1 cause neuronal degeneration is unclear. It was historically believed to be caused by aggregation and deposition of the affected protein similar to other polyglutamine expansion diseases, however rodent model studies have shown significantly later formation of nuclear inclusions of mutant proteins in cerebellum and spinal cord neurons than in cortical and hippocampal neurons, which typically show only mild degeneration in SCA1 persons, suggesting a more complicated mechanism. Ataxin-null mice are shown to exhibit reduced motor and spatial learning, suggesting ataxin 1 plays a role in synaptic plasticity and interactions between the motor neurons and the hippocampus.
It is not recommended in people with lupus erythematosus. Use during pregnancy may result in harm to the baby. Penicillamine works by binding heavy metals; the resulting penicillamine–metal complexes are then removed from the body in the urine.Bone marrow suppression, dysgeusia, anorexia, vomiting, and diarrhea are the most common side effects, occurring in ~20–30% of the patients treated with penicillamine.Other possible adverse effects include:

Nephropathy
Hepatotoxicity
Membranous glomerulonephritis
Aplastic anemia (idiosyncratic)
Antibody-mediated myasthenia gravis and Lambert–Eaton myasthenic syndrome, which may persist even after its withdrawal
Drug-induced systemic lupus erythematosus
Elastosis perforans serpiginosa
Toxic myopathies
Unwanted breast growth
Oligospermia

Chemistry
Penicillamine is a trifunctional organic compound, consisting of a thiol, an amine, and a carboxylic acid. It is structurally similar to the α-amino acid cysteine, but with geminal dimethyl substituents α to the thiol. Like most amino acids, it is a colorless solid that exists in the zwitterionic form at physiological pH. Penicillamine is a chiral drug with one stereogenic center and exist as a pair of enantiomers. Refer the image for the structure of penicillamine enantiomers. The (S)-enantiomer, the eutomer, is antiarthritic while the distomer (R)-penicillamine is extremely toxic. Of its two enantiomers, L-penicillamine (having R absolute configuration) is toxic because it inhibits the action of pyridoxine (also known as vitamin B6). That enantiomer is a metabolite of penicillin but has no antibiotic properties itself. A variety of penicillamine–copper complex structures are known. History
John Walshe first described the use of penicillamine in Wilsons disease in 1956.