Cystatin sequence

Salvesen, G., Parkes, C., Abrahamson, M., Grubb, A., and Barrett, A. J., Human low-Mr Kinino-gen contains three copies of a cystatin sequence that are divergent in structure and in inhibitory activity for cysteine proteinases. Biochem. J. 234(2), 129 131 (1986). 

To this list of protein misfolding diseases can be added rare familial amyloidoses in which the mutated proteins have the classic amyloid fibril congophilic birefringence and cross-(3-sheet structure (Table 3). Many of these deposits have an impact on the central nervous system (TTR, cystatin, lysozyme) as well as on other organ systems. A newly described disease, familial British dementia, is associated with the deposition of Abri, a 34 amino acid, 4 kDa peptide cleaved from a 277 amino acid precursor sequence, the last 10 amino acids of which are not normally translated [52]. Familial encephalopathy with neuroserpin inclusion bodies (FENIB) is... 

The N-terminal sequence of one peptide from the 35 kDa zone of H-gal-GP showed some homology to cathepsin B-like cysteine proteases. Molecular cloning has also identified a thrombospondin homologue associated with the diffusely staining region between zones A and B, a galectin associated with zone D (Newlands et al., 1999) and a low molecular weight (approximately 13 kDa) cysteine protease inhibitor, cystatin. 

A straightforward approach is to hunt for short polypeptides that meet the specificity requirement of an enzyme but which, because of peculiarities of the sequence, are acted upon very slowly. Such a peptide may contain unusual or chemically modified amino acids. For example, the peptide Thr-Pro-nVal-NMeLeu-Tyr-Thr (nVal=norvaline NMeLeu = N-methylleucine) is a very slow elastase substrate whose binding can be studied by X-ray diffraction and NMR spectroscopy.6 Thiol proteases are inhibited by succinyl-Gln-Val-Val-Ala-Ala-p-nitroanilide, which includes a sequence common to a number of naturally occurring peptide inhibitors called cystatins.f They are found in various animal tissues where they inhibit cysteine proteases. 

A family of cysteine proteinase inhibitors different from the cystatin super-family was Isolated from pineapple stem acetone powder. These inhibitors have a Mr of about 5800 and are composed of a longer (41 amino acids) and a shorter (1L ammo acids) peptide chain connected with disulfide bonds [29]. The conserved sequence Gin- fal-Val-AJa-Gly of the cystatins is not present in these inhibitors, indicating a different mechanism of interaction. The bromelain inhibitor VI was found to share similar folding and disulfide band connectivities with the Bowman-Bilk trypsiu/chymatrypsm inhibitor from soybean [30,31]. Hie physiological role of these inhibitors remains undear. 

His1 0 and orients it for its catalytic function [54], The putative catalytic thiolate-imldazollum pair at the active site of bromelain is thus, by comparison of the amino acid sequence of bromelain with other cysteine protein ases, likely to have a different conformation from that in (he cysteine proteinases (hat aie tightly inhibited by cystatin [45]. Bromelain also distinguishes itself from other cysteine protein ases by its slow inhibition by the irreversible inhibitor of cysteine oroteinases E-64 rW-ft 3-fraw-cari)OKVOxiran-2 BrboiwlVL-leucvn-amido 4-... 

Rogers, B.L., Pollock, J., Klapper, D.G., and Griffith, IJ. 1993. Sequence of the proteinase-inhibitor cystatin homologue from the pollen of Ambrosia artemisiifolia (short ragweed). Gene 133 219-221. 

Fig. 1. Amino acid sequence and schematic structure of human cystatin C. The shaded area marks the inhibitory site for papain-like cysteine proteases, which does not overlap with the inhibitory site for mammalian legumains comprising, inter alia, the Asn39 residue. The arrow indicates the Leu68 residue, which is replaced with a Gin residue in the cerebral hemorrhage producing cystatin C variant. The asterisk marks the Pro3 residue, which is partly hydroxylated.

The complete amino acid sequence of the single polypeptide chain of human cystatin C was determined in 1981 (Gil) and later corroborated by identification and sequencing of the corresponding cDNA (Fig. 4) (A3) and gene (A5, A7). 

DNA sequence The nucleotide sequence data are available from the EMBL, GenBank, and DDBJ Nucleotide Sequence Databases under accession number X52255 Half-life About 20 min (experimentally determined for human cystatin C in rat plasma. The similarity in distribution volume and renal clearance between human cystatin C and acknowledged markers of human glomerular filtration, i.e., iohexol and 51 Cr-EDTA, suggests that the substances are eliminated at the same rate in humans with a half-life of approximately 2 h in individuals with normal renal function)... 

A3. Abrahamson, M., Grubb, A., Olafsson, I., and Lundwall, A., Molecular cloning and sequence analysis of cDNA coding for the precursor of the human cysteine proteinase inhibitor cystatin... 

D3. Delbridge, M. L., and Kelly, L. E., Sequence analysis, and chromosomal localization of a gene encoding a cystatin-like protein from Drosophila melanogasler. FEBS Lett. 274(1-2), 141-145... 

T10. Turk, V., Brzin, J., Longer, M., Ritonja, A., Eropkin, M., et al., Protein inhibitors of cysteine proteinases. III. Amino-acid sequence of cystatin from chicken egg white. Hoppe Seylers Z. Physiol. Chem. 364(11), 1487-1496(1983). 

The initial assays for detection of CB used chromogenic substrates containing an Arg-Arg sequence and 2-naphthyl-amide and 7-amino-4-methylcoumarin as chromophores. These early assays lacked specificity and were likely to have suffered from interference by endogenous uihibitors (e.g., cystatins and stefins). CB and CL are now measured by ELISA however to date no comparison has been made with the older CB methods. Immunohistochemistry has also been used to detect CB in tissue however no detailed evaluations have been conducted. 

A. Ritonja, A. D. Rowan, D. J. Buttle, N. D. Rawlings, V. Turk, and A. J. Barrett. Stem bromelain amino acid sequence and implications for weak binding of cystatin. FEBS Lett. 247 419 (1989). 

Aside from telomeric sequences and c-myc, discussed elsewhere in this book, other known quadruplex-forming sequences include the fragile X syndrome repeat d(CGG) and the Cystatin B promoter, which has a region with sequence (CGCG4CG4)4 and is involved in epilepsy. G-rich strands of the... 

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