Involvement of Tyr108 in the enzyme mechanism of the small laccase from Streptomyces coelicolor.

The enzyme mechanism of the multicopper oxidase (MCO) SLAC from Streptomyces coelicolor was investigated by structural (XRD), spectroscopic (optical, EPR), and kinetics (stopped-flow) experiments on variants in which residue Tyr108 had been replaced by Phe or Ala through site-directed mutagenesis. Contrary to the more common three-domain MCOs, a tyrosine in the two-domain SLAC is found to participate in the enzyme mechanism by providing an electron during oxygen reduction, giving rise to the temporary appearance of a tyrosyl radical. The relatively low k(cat)/K(M) of SLAC and the involvement of Y108 in the enzyme mechanism may reflect an adaptation to a milieu in which there is an imbalance between the available reducing and oxidizing co-substrates.

Structure of a post-translationally processed heterodimeric double-headed Kunitz-type serine protease inhibitor from potato.

Potato serine protease inhibitor (PSPI) constitutes about 22% of the total amount of proteins in potato tubers (cv. Elkana), making it the most abundant protease inhibitor in the plant. PSPI is a heterodimeric double-headed Kunitz-type serine protease inhibitor that can tightly and simultaneously bind two serine proteases by mimicking the substrate of the enzyme with its reactive-site loops.

Crystal structure of chlorite dismutase, a detoxifying enzyme producing molecular oxygen.

Chlorite dismutase (Cld) is a key enzyme of perchlorate and chlorate respiration. This heme-based protein reduces the toxic compound chlorite into the innocuous chloride anion in a very efficient way while producing molecular oxygen. A sequence comparison between Cld homologues shows a highly conserved family.

Involvement of a carboxylated lysine in UV damage endonuclease.

UV damage endonuclease is a DNA repair enzyme that can both recognize damage such as UV lesions and introduce a nick directly 5' to them. Recently, the crystal structure of the enzyme from Thermus thermophilus was solved. In the electron density map of this structure, unexplained density near the active site was observed at the tip of Lys229.

Characterization of a diagnostic Fab fragment binding trimeric Lewis X.

Lewis X trisaccharides normally function as essential cell-cell interaction mediators. However, oligomers of Lewis X trisaccharides expressed by the parasite Schistosoma mansoni seem to be related to its evasion of the immune response of its human host. Here we show that monoclonal antibody 54-5C10-A, which is used to diagnose schistosomiasis in humans, interacts with oligomers of at least three Lewis X trisaccharides, but not with monomeric Lewis X.

Cloning, expression, purification, crystallization and preliminary X-ray diffraction analysis of chlorite dismutase: a detoxifying enzyme producing molecular oxygen.

Chlorite dismutase, a homotetrameric haem-based protein, is one of the key enzymes of (per)chlorate-reducing bacteria. It is highly active (>2 kU mg(-1)) in reducing the toxic compound chlorite to the innocuous chloride anion and molecular oxygen. Chlorite itself is produced as the intermediate product of (per)chlorate reduction.

Protonation of a histidine copper ligand in fern plastocyanin.

Plastocyanin is a small blue copper protein that shuttles electrons as part of the photosynthetic redox chain. Its redox behavior is changed at low pH as a result of protonation of the solvent-exposed copper-coordinating histidine. Protonation and subsequent redox inactivation could have a role in the down regulation of photosynthesis.

The protein structure of recombinant human lactoferrin produced in the milk of transgenic cows closely matches the structure of human milk-derived lactoferrin.

Human lactoferrin (hLF) is an iron-binding glycoprotein involved in the host defence against infection and excessive inflammation. As the availability of (human milk-derived) natural hLF is limited, alternative means of production of this biopharmaceutical are extensively researched. Here we report the crystal structure of recombinant hLF (rhLF) expressed in the milk of transgenic cows at a resolution of 2.

Crystallization and preliminary X-ray crystallographic studies on a Kunitz-type potato serine protease inhibitor.

Interest in protease inhibitors has been renewed because of their potent activity in preventing carcinogenesis in a wide variety of in vivo and in vitro model systems. Potato tubers contain a wide range of such protease inhibitors. In cv.