title: Oculocutaneous albinism type 1: link between mutations, tyrosinase conformational stability, and enzymatic activity.
abstract: Oculocutaneous albinism type 1 (OCA1) is an autosomal recessive disorder caused by mutations in the tyrosinase gene. Two subtypes of OCA1 have been described: severe OCA1A with complete absence of tyrosinase activity and less severe OCA1B with residual tyrosinase activity. Here, we characterize the recombinant human tyrosinase intramelanosomal domain and mutant variants, which mimic genetic changes in both subtypes of OCA1 patients. Proteins were prepared using site-directed mutagenesis, expressed in insect larvae, purified by chromatography, and characterized by enzymatic activities, tryptophan fluorescence, and Gibbs free energy changes. The OCA1A mutants showed very low protein expression and protein yield and are enzymatically inactive. Mutants mimicking OCA1B were biochemically similar to the wild type, but exhibited lower specific activities and protein stabilities. The results are consistent with clinical data, which indicates that OCA1A mutations inactivate tyrosinase and result in severe phenotype, while OCA1B mutations partially inactivate tyrosinase and result in OCA1B albinism.
authors: National Eye Institute, National Institutes of Health, Bethesda, MD, USA.
authors: Monika B
authors: MB
authors: Dolinska
authors: National Eye Institute, National Institutes of Health, Bethesda, MD, USA.
authors: Nicole J
authors: NJ
authors: Kus
authors: National Eye Institute, National Institutes of Health, Bethesda, MD, USA.
authors: S Katie
authors: SK
authors: Farney
authors: National Institute of Artritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD, USA.
authors: Paul T
authors: PT
authors: Wingfield
authors: National Eye Institute, National Institutes of Health, Bethesda, MD, USA.
authors: Brian P
authors: BP
authors: Brooks
authors: National Eye Institute, National Institutes of Health, Bethesda, MD, USA.
authors: Yuri V
authors: YV
authors: Sergeev
mesh_terms: D016115:Albinism, Oculocutaneous / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D002384:Catalysis; D006801:Humans; D008958:Models, Molecular; D014442:Monophenol Monooxygenase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D009154:Mutation / Q000235:genetics*; D011487:Protein Conformation; D017510:Protein Folding; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D011994:Recombinant Proteins; D014442:Monophenol Monooxygenase
keywords: genetic mutations; oculocutaneous albinism; protein purification; protein stability; protein structure; protein unfolding; tyrosinase