Cloning, Escherichia coli expression, purification, characterization, and enzyme assay of the ribosomal protein S4 from wheat seedlings (Triticum vulgare)

► We describe production of wheat ribosomal protein S4 in Escherichia coli. ► The 265-amino acid protein is a hitherto unknown cysteine protease. ► It hydrolyzes cysteine protease-specific peptide-based substrates. ► The proteolytic nature could be related to extraribosomal function of S4.