Keratin, type I cuticular Ha3-I is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...

that in humans is encoded by the ''KRT33A''

gene In biology, the word gene (from , ; "... Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

. The protein encoded by this gene is a member of the keratin gene family. It is one of the type I hair keratin genes which are clustered in a region of chromosome 17q12-q21 and have the same direction of transcription. As a type I hair keratin, it is an acidic protein which heterodimerizes with type II keratins to form hair and nails. There are two isoforms of this protein, encoded by two separate genes, KRTHA3A and KRTHA3B.

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