Structural analysis of the effects of mutations in Ubl domain of Parkin leading to Parkinson's disease.

Parkinson's disease (PD) is characterized by progressive death of dopamine producing neurons in the substantia nigra pars compacta of the mid brain. Dysfunction of an E3 ligase protein, Parkin, encoded by PARK2 gene, results in accumulation of misfolded proteins in brain cells which lead to the onset of PD. Parkin is a multi-domain protein consisting of N-terminal ubiquitin-like domain (Ubl) followed by RING0, RING1, In Between Ring (IBR) domain and RING2 domain which is present at the C-terminal end of Parkin protein. Ubl domain is the smallest domain of Parkin and is involved in the binding of Parkin with E2 protein molecule required for proper Ubiquitination and functioning of proteins in the brain. Mutations in the Parkin protein are known to be associated with protein dysfunction leading to PD. This study aims to decipher the characteristics and effects of the different mutations in the Ubl domain by an in-silico analysis. The mutations were collected from PDmutDB and COSMIC databases. The pathogenic impacts of amino-acid mutations on Ubl structure and function were analysed by using various computational tools. Due to lack of proper full-chain structure of the Ubl domain, a homology model of the domain was reconstructed using Discovery Studio 2.5 (DS 2.5) software suite. We found that the mutations A31D, A46P, C59F, A46T, E28K, E49K, R42P, R42S, and Q63K were the most deleterious ones which might be associated with the onset of PD. In order to study the dynamic behaviour of the Parkin Ubl domain in cellular environment, molecular dynamics (MD) simulations were carried out using the wild-type and mutant Ubl domains. Our analyses could predict the cellular dynamics of the mutations and therefore might help in predicting the hitherto unknown molecular mechanism of the disease onset and designing precision medicine for the treatment of PD.