Enhanced expression of chicken cystatin as a thioredoxin fusion form in Escherichia coli AD494(DE3)pLysS and its effect on the prevention of surimi gel softening

Egg White Cystatin – A Review

Hen eggs are widely used, not only for human consumption, but also as an important material in food production and in pharmaceutical and cosmetics industry. Cystatin is a biologically active component of egg white, mostly used as an inhibitor of papain-like cysteine proteases. It was isolated from chicken egg white and has later been used in the nomenclature of structurally and functionally related proteins. Cystatins from animals, including mouse, rat, dog, cow and chicken egg white have been isolated and recently used in foodstuffs and drug administration. Cystatin has found its place and use in medicine due to its antimicrobial, antiviral and insecticidal effects, for the prevention of cerebral hemorrhage and control of cancer cell metastasis.

Molecular Cloning, Expression, and Functional Characterization of a Cystatin from Pineapple Stem

A cDNA fragment encoding the cysteine protease inhibitor, cystatin, was cloned from pineapple (Ananas comosus) stem. This clone was constructed in a fusion vector and was easily over-expressed in Escherichia coli; satisfactory over-expression of non-fusion cystatin was achieved after an additional start codon was inserted prior to its coding sequence. Both recombinant cystatins were predominately found in the soluble fraction of the cell extract, and were demonstrated to be functionally active in a reverse zymographic assay. The fusion and non-fusion cystatins were separately purified to homogeneity via a His-tag or papain-coupling affinity column. Effective inhibitory activity against papain was detected with both the fusion and non-fusion cystatins with comparable K(i) values of 1.18 x 10(-10) M and 9.53 x 10(-11) M, respectively. The recombinant cystatins were found to be thermally stable up to 60 degrees C. Inhibition of the endogenous protease activity in minced fish muscle revealed that the recombinant pineapple cystatins might be an adequate stabilizer to prevent protein degradation during industrial food processing.

Binding of glycated ovocystatin to rat renal brush border membranes

Glycated proteins are considered as one of the factors involved in the pathogenesis of diabetic complications, including nephropathy. These proteins are formed endogenously under conditions of hyperglycemia, as well as being provided with food containing sugars, which was subjected to high temperature. Examples are egg products. One of the proteins found in eggs in a relatively high concentration is chicken cystatin (ovocystatin). It is now believed that some proteins can passage the intestinal epithelium by transcytosis directly into the bloodstream. Thus, glycated protein present in food can be an additional source of glycotoxins. The aim of this study was to compare the affinity of native and glycated cystatin to the brush border membranes of rat kidney. Kinetic analysis was performed with surface plasmon resonance technique using sensor chip L1. Dissociation constants for native and glycated cystatin (Kd ) were 2.76 μmol/L and 3.82 μmol/L, respectively. The results of our study indicate that glycation only slightly affects binding of cystatin to brush border membranes. This suggests that glycated cystatin and other glycated proteins may also be efficiently taken up in the kidney proximal tubule. The observation may be important for understanding the mechanisms involved in the development of diabetic nephropathy.

Application of recombinant chum salmon cystatin to Alaska pollock (Theragra chalcogramma) surimi to prevent gel weakening

Recombinant chum salmon cystatin (RC) expressed in Saccharomyces cerevisiae was purified by His-select nickel affinity chromatography. The specific inhibitory activities of RC against papain and cathepsin L were 7.45 and 10.24 U/mg, respectively. RC was stable over pH 5.0 to 7.0 and at temperature below 65 degrees C. RC was used to prevent the gel weakening of Alaska pollock surimi. RC at 100 microg/g showed the highest inhibitory activity against the autolysis of surimi based on the analysis of TCA-soluble peptides. As the concentration of RC increased, both the breaking force and deformation of modori gel greatly increased (P < 0.05). The addition of RC resulted in less expressible drip, which coincided with the increase of whiteness. More myosin heavy chain (MHC) was retained as the addition of RC increased. Therefore, RC could prevent the degradation of proteins in Alaska pollock surimi and was better than egg white (EW). Thus, RC could be applied to Alaska pollock surimi to prevent gel weakening and RC at 100 microg/g was the optimal concentration.

Cloning of a cDNA encoding a cystatin from grain amaranth (Amaranthus hypochondriacus) showing a tissue-specific expression that is modified by germination and abiotic stress

A cDNA, encoding a cysteine protease inhibitor (AhCPI), was isolated from an immature seed cDNA library of grain amaranth (Amaranthus hypochondriacus L.) and characterized. It encoded a polypeptide of 247 amino acids (aa), including a putative N-terminal signal peptide. Other relevant regions found in its sequence included the G and PW conserved aa motifs, the consensus LARFAV sequence for phytocystatins and the reactive site QVVAG. The predicted aa sequence for AhCPI showed a significant homology to other plant cystatins. Gene expression analyses indicated that AhCPI was constitutively expressed in mature seeds, and gradually decreased during germination. In vegetative tissues, AhCPI was expressed in the radicle and hypocotyls of seedlings and in the stems and roots of young plantlets. Its expression in roots and stems increased substantially in response to water deficit, salinity-, cold- and heat-stress, whereas heat-stress induced a rapid and transient accumulation of AhCPI transcripts in leaves. The results obtained were suggestive of multiple roles for AhCPI in grain amaranth, acting as a regulator of seed germination and as a protective agent against diverse types of abiotic stress, which induced this gene in a tissue- and stress-specific manner. The work herewith described reports a novel, and apparently, single cystatin protein in which, in agreement with other plant model systems, could have a regulatory role in germination, and further expands previous findings linking the accumulation of protease inhibitors, mostly of the serine proteinase type, with protection against (a)biotic stress in A. hypochondriacus.

High-level expression of a soluble and functional fibronectin type II domain from MMP-2 in the Escherichia coli cytoplasm for solution NMR studies

We report a method for the expression in Escherichia coli of the isolated second type II fibronectin domain from MMP-2 (FNII-2). FNII-2 was expressed as a His(6)thioredoxin-tagged fusion protein in the thioredoxin reductase deficient E. coli strain BL21trxB(DE3), thus allowing disulfide-bond formation. When cultured at 37 degrees C, the expressed protein is located exclusively in the soluble fraction of the E. coli lysate. The fusion protein from the soluble fraction was purified and the His(6)thioredoxin-tag was cleaved by thrombin, resulting in a yield of approximately 40 mg/L. The recombinant FNII-2 was demonstrated to be functional by its ability to bind to gelatin-Sepharose, correct folding of the purified protein was confirmed by NMR spectroscopy. This approach may generally be applicable to all FNII domains and is a significant simplification relative to existing techniques involving refolding from inclusion bodies or expression in the eukaryotic host, Pichia pastoris.

Molecular cloning, sequencing, expression of Chinese sturgeon cystatin in yeast Pichia pastoris and its proteinase inhibitory activity

Cystatin, a superfamily of cysteine proteinase inhibitor of cathepsins and other cysteine proteinases, is widely distributed in animal tissues and body fluids. Although considerable attention has been given to mammalian and avian cystatins, little is known about cystatins from other vertebrates. In this study, a cDNA coding for Chinese sturgeon (Acipenser sinensis) cystatin was isolated and characterized. The corresponding mature cystatin peptide cDNA is 336 nucleotides long and encodes a protein of 112 amino acids. Sequence comparison showed that the cloned cystatin was a homolog of the mammalian Family II cystatin. The cystatin cDNA of Chinese sturgeon was subcloned into yeast expression vector pPICZalphaA and transformed into Pichia pastoris GS115 strain. After methanol induction, SDS-PAGE analysis of the culture supernatant indicated that the yield of recombinant cystatin was about 215 mg/l medium supernatant in shaking-flask fermentation medium, accounting for 73.6% of the total supernatant secreted proteins. Our data also showed that the recombinant cystatin is active in inhibiting the protease activity of papain and cathepsin B. Heat stability of the recombinant cystatin was also measured.

Purification and determination of inhibitory activity of recombinant soyacystatin for surimi application

A recombinant soyacystatin (r-soyacystatin) was tested for its inhibitory activity against cysteine proteinase of Pacific whiting and its activity was compared to that of egg white cystatin. A recombinant soyacystatin expressed in Escherichia coli was purified to electrophoretic homogeneity using phenyl-Sepharose and DEAE-Sepharose. Native egg white cystatin was purified by using affinity chromatography on CM-papain-Sepharose generated in our lab. Egg white cystatin and soyacystatin were tested for proteinase inhibitory activity against commercial papain and also cathepsin L purified from Pacific whiting muscle. The r-soyacystatin exhibited papain-like protease inhibition activity comparable to that of the egg white cystatin, which could inhibit papain and Pacific whiting cathepsin L. The r-soyacystatin subsequently inhibited the autolytic activity of Pacific whiting surimi.