Cystatins are natural tight-binding reversible inhibitors of cysteine proteases. In this study, a cDNA library was constructed from Collichthys lucidus using the SMART technique. A complete cDNA sequence with high identity to the conserved sequence of the cystatin C gene was cloned from the library using EST analysis and rapid amplification of cDNA ends (RACE), then subjected to further investigation. The full-length cDNA of cystatin C from C.
Human cystatin C (CysC) is a cysteine proteinase inhibitor with many potential applications. To facilitate further studies of the functions and applications of CysC, we improved the heterologous expression of CysC using a basic codon optimization method. In this study, we cloned the high-GC content wild-type sequence of the CysC gene and also designed a slightly AT-biased sequence, with codons optimized for expression in the Pichia pastoris GS115 strain.