| The cystatins are tightly binding, but reversible, inhibitors of cysteine proteinases, which constitute a superfamily of evolutionary related proteins. They have been subdivided into three families: the cystatin family which contain two disulfide bonds, the stefin family which lack disulfide bonds, and the kininogen family composed of large glycoproteins containing three repeats similar to those found in the cystatin family. Members of the cystatin superfamily occurring in plants are currently known as phytocystatins, defined as proteins lacking disulfide bonds but possessing a conserved N-terminal amino acid sequence (L-A-R-[FY]-A-[VI]-X(3)-N). We have used the protein sequence deduced from seven phytocystatins (from the Arabidopsis thaliana genome... |
