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A single amino acid substitution affects substrate specificity in cysteine proteinases from Fasciola hepatica.

ABSTRACT: The trematode Fasciola hepatica secretes a number of cathepsin L-like proteases that are proposed to be involved in feeding, migration, and immune evasion by the parasite. To date, six full cDNA sequences encoding cathepsin L preproproteins have been identified. Previous studies have demonstrated that one of these cathepsins (L2) is unusual in that it is able to cleave substrates with a proline in the P2 position, translating into an unusual ability (for a cysteine proteinase) to clot fibrinogen. In this study, we report the sequence of a novel cathepsin (L5) and compare the substrate specificity of a recombinant enzyme with that of recombinant cathepsin L2. Despite sharing 80% sequence identity with cathepsin L2, cathepsin L5 does not exhibit substantial catalytic activity against substrates containing proline in the P2 position. Molecular modeling studies suggested that a single amino acid change (L69Y) in the mature proteinases may account for the difference in specificity at the S2 subsite. Recombinant cathepsin L5/L69Y was expressed in yeast and a substantial increase in the ability of this variant to accommodate substrates with a proline residue in the P2 position was observed. Thus, we have identified a single amino acid substitution that can substantially influence the architecture of the S2 subsite of F. hepatica cathepsin L proteases.

SUBMITTER: Smooker PM

PROVIDER: S-EPMC2144524 | biostudies-other | 2000 Dec

REPOSITORIES: biostudies-other

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A single amino acid substitution affects substrate specificity in cysteine proteinases from Fasciola hepatica.

Smooker P M PM Whisstock J C JC Irving J A JA Siyaguna S S Spithill T W TW Pike R N RN

Protein science : a publication of the Protein Society 20001201 12

The trematode Fasciola hepatica secretes a number of cathepsin L-like proteases that are proposed to be involved in feeding, migration, and immune evasion by the parasite. To date, six full cDNA sequences encoding cathepsin L preproproteins have been identified. Previous studies have demonstrated that one of these cathepsins (L2) is unusual in that it is able to cleave substrates with a proline in the P2 position, translating into an unusual ability (for a cysteine proteinase) to clot fibrinogen ...[more]

PMID: 11206078

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Project description:BackgroundFasciola hepatica (liver fluke) affects grazing animals including horses but the extent to which it affects UK horses is unknown.ObjectivesTo define how liver fluke affects the UK horse population.Study designDescriptive, cross-sectional, observational study.MethodsAn F. hepatica excretory-secretory antibody detection ELISA with a diagnostic sensitivity of 71% and specificity of 97% was validated and used to analyse serum samples. An abattoir study was performed to determine prevalence. A case-control study of 269 horses compared fluke exposure between horses with liver disease and controls. Data on clinical signs and blood test results were collected for sero-positive horses. Genotyping of adult fluke was used to produce a multilocus genotype for each parasite.ResultsFour (2.2%) of 183 horses registered in the UK, sampled in the abattoir, had adult flukes in the liver, and the sero-prevalence of F. hepatica was estimated as 8.7%. In the case-control study, horses showing signs consistent with liver disease had significantly higher odds of testing positive for F. hepatica on ELISA than control horses. In 23 sero-positive horses, a range of non-specific clinical signs and blood test abnormalities was reported, with a third of the horses showing no signs. Genotypic analysis of liver flukes from horses provided evidence that these came from the same population as flukes from sheep and cattle.Main limitationsBias could have arisen in the prevalence and case-control studies due to convenience sampling methods, in particular the geographic origin of the horses. Only a small number of horses tested positive so the data on clinical signs are limited.ConclusionsExposure to liver fluke occurs frequently in horses and may be an under-recognised cause of liver disease. Flukes isolated from horses are from the same population as those found in ruminants. When designing and implementing parasite control plans, fluke should be considered, and horses should be tested if appropriate.

Dataset Information

A single amino acid substitution affects substrate specificity in cysteine proteinases from Fasciola hepatica.

Publications

A single amino acid substitution affects substrate specificity in cysteine proteinases from Fasciola hepatica.

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