title: Review: The future of cystatin engineering.
abstract: Plant cystatins are naturally occurring protease inhibitors that prevent proteolysis by papain-like cysteine proteases. Their protective action against environmental stresses has been relatively well characterised. Still, there is a need to greatly improve both potency and specificity based on the current rather poor performance of cystatins in biotechnological applications. Research in creating more potent and specific cystatins, including amino acid substitutions in either conserved cystatin motifs and/or at variable amino acid sites, is reviewed. Existing gaps for better understanding of cystatin-protease interactions are further explored. Current knowledge on multi-cystatins or hybrid protease inhibitors involving cystatins as an additional option for cystatin engineering is further outlined along with the nuances of how cystatins with rather unusual amino acid sequences might actually help in cystatin engineering. Finally, future opportunities for application of cystatins are highlighted which include applications in genetically modified transgenic plants for environmental stress protection and also as nutraceuticals, as part of more nutritious food. Further opportunities might also include the possible management of diseases and disorders, often associated with lifestyle changes, and the most immediate and promising application which is inclusion into plant-based recombinant protein production platforms.
authors.affiliation: Department of Plant Production and Soil Science, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria 0002, South Africa.
authors.forename: Stefan G
authors.initials: SG
authors.lastname: van Wyk
authors.affiliation: Department of Plant Science, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria 0002, South Africa. Electronic address: karl.kunert@up.ac.za.
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Kunert
authors.affiliation: Department of Biology, Case Western Reserve University, Cleveland, OH 44106-7080, USA.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: Cullis
authors.affiliation: Department of Plant Science, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria 0002, South Africa.
authors.forename: Priyen
authors.initials: P
authors.lastname: Pillay
authors.affiliation: Department of Plant Science, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria 0002, South Africa.
authors.forename: Matome E
authors.initials: ME
authors.lastname: Makgopa
authors.affiliation: Department of Plant Science, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria 0002, South Africa.
authors.forename: Urte
authors.initials: U
authors.lastname: Schlüter
authors.affiliation: Department of Plant Production and Soil Science, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria 0002, South Africa.
authors.forename: Barend J
authors.initials: BJ
authors.lastname: Vorster
mesh_terms: D015891:Cystatins / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D015202:Protein Engineering / Q000379:methods*; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D015891:Cystatins; D015853:Cysteine Proteinase Inhibitors; D011994:Recombinant Proteins
keywords: Cystatin; Cystatin engineering; Multi-cystatins; Phytocystatin; Plant; Protease inhibitor; Proteolysis