Influence of pH and ionic strength on the lysis of Micrococcus luteus cells by hen lysozyme at low (20 degree C) and high (physiological, 40 degree C) temperature

Effect of inhibitors on conformational changes in hen lysozyme around thermal transition point in solution and solid state

Carbon-13 NMR spectroscopy has been used to further document the interaction, at low and high temperatures, of N-acetylglucosamine and its short polymers with hen egg-white lysozyme. The results have been compared with the corresponding X-ray crystallographic data. Two domains, the active site and the hydrophobic box, have been found by NMR to undergo conformational rearrangement while X-ray crystallography only detected changes located in the active site. The extent of the modifications induced by inhibitor binding was proportional to the inhibitor size. The two techniques concurred to show that even in the presence of monosaccharide (N-acetylglucosamine), more than one subsite of the enzyme was occupied at high temperature, the binding at the C-site being the best defined. The thermal transition of lysozyme still occurred in solution when inhibitors were bound. However, in the solid state, crystallographic data showed that the transition was hindered.

N.m.r. study of conformational changes in lysozyme around the thermal transition point

Natural abundance carbon-13 n.m.r. at 50.3 MHz has been used to further document the thermal transition that hen egg-white lysozyme undergoes in solution between 20 degrees and 30 degrees. The study focuses on the temperature sensitivity of more than 50 carboxylic, aromatic and aliphatic single carbon resonances for which unambiguous assignments to specific residues are known. The analysis of selective perturbations in chemical shifts indicates that residues located on both edges of the active site cleft and in the hydrophobic box are primarily involved in the temperature-induced conformational transition. N.m.r. results are compared with crystallographic data on low temperature (form A) and high temperature (form B) interconverting lysozyme crystals, taking advantage of the recent availability of quality high resolution maps for B form orthorhombic crystals. In most cases, a good correlation is found at the atomic level between residues involved in the thermal transition in solution and in the crystalline state. Discrete discrepancies are noted for some residues such as Trp-62 and His-15.

What's new in lysozyme research? Always a model system, today as yesterday

The present review is focused on the main achievements realized in the lysozyme research field since the meeting held in 1972 to commemorate the fiftieth anniversary of the discovery of this enzyme. Despite of extensive structural, physico-chemical, crystallographic, genetic, immunological and evolutionary studies devoted to lysozymes, their biological role is still not exactly known.