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PubMed1987

The high-resolution X-ray crystal structure of the complex formed between subtilisin Carlsberg and eglin c, an elastase inhibitor from the leech Hirudo medicinalis. Structural analysis, subtilisin structure and interface geometry.

Triclinic crystals of the complex formed by eglin with subtilisin Carlsberg were analyzed by X-ray diffraction. The crystal and molecular structure of this complex was determined with data that extended to 0.12-nm resolution by a combination of Patterson search methods and isomorphous replacement techniques. Its structure was refined to a crystallographic R value of 0.178 (1.0-0.12 nm) using an energy-restraint least-squares procedure. The complete subtilisin molecule could be traced without ambiguity in the refined electron density. The eglin component, from which an amino-terminal segment is cleaved off, is only defined from Lys8I (i.e. the lysine residue 8 of the inhibitor) onwards. Per unit cell, 436 fixed solvent molecules and 2 calcium ions were located. In spite of 84 amino acid replacements and one deletion, subtilisin Carlsberg exhibits a very similar polypeptide fold to subtilisin BPN'. The root-mean-square deviations of all alpha-carbon atoms (excluding those at the deletion site) from models of subtilisin BPN' [Alden, R. A., Birktoft, J. J., Kraut, J., Robertus, J. D. & Wright, C. S. (1971) Biochem. Biophys. Res. Commun. 45, 337-344] and subtilisin Novo [Drenth, J., Hol, W. G. J., Jansonius, J. N. & Kockoek, R. (1972) Eur. J. Biochem. 25, 177-181] are 0.077 nm and 0.103 nm. Most of these deviations result from global shifts rather than changes of the local geometry. The single-residue deletion at position 56 affects only the surrounding conformation. Two sites of high electron density and close distances to surrounding oxygen ligands have been found in the Carlsberg enzyme which are probably occupied by calcium ions. Eglin consists of a twisted four-stranded beta-sheet flanked by an alpha-helix and by an exposed proteinase binding loop on opposite sides. Around the reactive site, Leu45I-Asp46I, this loop is mainly stabilized by electrostatic/hydrogen bond interactions with the side chains of two arginine residues which project from the hydrophobic core [Bode, W., Papamokos, E., Musil, D., Seemüller, W. & Fritz, H. (1986) EMBO J. 5, 813-818]. The reactive site loop conformation resembles that found in other 'small' proteinase inhibitors. The scissile peptide bond is not cleaved but its carbonyl group is slightly distorted from planar geometry. Most of the intermolecular contacts are contributed by the nine residues of the reactive-site loop Gly40I-Arg48I.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1991

Yolk protein in leech. Identification, purification and characterization of vitellin and vitellogenin.

Theromyzon tessulatum vitellin was identified as a lipoglycoprotein of 490 kDa. The insolubility of this molecule in low-ionic-strength media was used to extract it from the ovaries. Antiserum prepared against vitellin was shown to react with a coelomic fluid component of 520 kDa. This vitellin precursor, or vitellogenin, was purified by gel permeation and ion-exchange column chromatography. These two lipoglycoproteins were characterized by amino acid, carbohydrate and lipid analysis and subunit composition. In spite of differences in terms of native molecular mass, solubility and isoelectric point, the lipoglycoproteins isolated from the coelomic fluid and the ovary were similar in their subunit components (a single polypeptide of 165 kDa) and in their amino acid and carbohydrate compositions. However, vitellogenin was found to be more highly lipidated (31.8% by mass) than vitellin (24% by mass) and lipid analysis indicated a higher amount of sterols and phospholipids in vitellogenin. From these data, we conclude that vitellogenin and vitellin are probably dimers of two identical subunit polypeptides plus lipid and that, after vitellogenin is sequestered in the oocyte, part of its lipid component is stripped from the molecule to give vitellin. Furthermore, electrophoretic analysis seems to indicate that vitellogenin synthesis and secretion is initiated following the third and last blood meal of the animal but that vitellogenin significantly accumulates in the coelomic fluid before being incorporated in the oocytes suggesting a complex mode of vitellogenesis regulation.

Amino Acids↗
PubMed2001

Leech jar.

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Animals↗
PubMed2005

History of evidence-based medicine. Oranges, chloride of lime and leeches: barriers to teaching old dogs new tricks.

Knowledge translation is the process of taking evidence from research and applying it in clinical practice. In this article I will cite some pivotal moments in the history of medicine to highlight the difficulties and delays associated with getting evidence into practice. These historical examples have much in common with modern medical trials and quality improvement processes. I will also review the reasons why evidence is not used and consider what factors facilitate the uptake of evidence. Understanding these concepts will make it easier for individual clinicians and institutions to change clinical behaviour and provide a starting point for those looking at implementing 'new' practices, new therapies and clinical guidelines. Finally, I will offer a list of criteria that clinicians might choose to consider when deciding on whether or not to adopt a new practice, treatment or concept.

Animals↗