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Oculocutaneous albinism type 1: link between mutations, tyrosinase conformational stability, and enzymatic activity
Author(s) -
Dolinska Monika B.,
Kus Nicole J.,
Farney S. Katie,
Wingfield Paul T.,
Brooks Brian P.,
Sergeev Yuri V.
Publication year - 2017
Publication title -
pigment cell and melanoma research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.618
H-Index - 105
eISSN - 1755-148X
pISSN - 1755-1471
DOI - 10.1111/pcmr.12546
Subject(s) - tyrosinase , oculocutaneous albinism , albinism , mutant , mutagenesis , mutation , biochemistry , wild type , biology , microbiology and biotechnology , enzyme , gene , chemistry , genetics
Summary Oculocutaneous albinism type 1 ( OCA 1) is an autosomal recessive disorder caused by mutations in the tyrosinase gene. Two subtypes of OCA 1 have been described: severe OCA 1A with complete absence of tyrosinase activity and less severe OCA 1B with residual tyrosinase activity. Here, we characterize the recombinant human tyrosinase intramelanosomal domain and mutant variants, which mimic genetic changes in both subtypes of OCA 1 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 OCA 1A mutants showed very low protein expression and protein yield and are enzymatically inactive. Mutants mimicking OCA 1B 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 OCA 1A mutations inactivate tyrosinase and result in severe phenotype, while OCA 1B mutations partially inactivate tyrosinase and result in OCA 1B albinism.