Heat-shock-induced proteins from Myxococcus xanthus

Optimal conditions for two-dimensional gel electrophoresis of total cellular proteins from Myxococcus xanthus were established. Using these conditions, we analyzed protein patterns of heat-shocked M. xanthus cells. Eighteen major spots and 15 minor spots were found to be induced by heat shock. From N-terminal sequences of 15 major spots, DnaK, GroEL, GroES, alkyl hydroperoxide reductase, aldehyde dehydrogenase, succinyl coenzyme A (CoA) synthetase, 30S ribosomal protein S6, and ATP synthase alpha subunit were identified. Three of the 18 major spots had an identical N-terminal sequence, indicating that they may be different forms of the same protein. Although a DnaK homologue, SglK, has been identified in M. xanthus (R. M. Weimer, C. Creghton, A. Stassinopoulos, P. Youderian, and P. L. Hartzell, J. Bacteriol. 180:5357-5368, 1998; Z. Yang, Y. Geng, and W. Shi, J. Bacteriol. 180:218-224, 1998), SglK was not induced by heat shock. In addition, there were seven substitutions within the N-terminal 30-residue sequence of the newly identified DnaK. This is the first report to demonstrate that succinyl CoA synthetase, 30S ribosomal protein S6, and ATP synthase alpha subunit are heat shock inducible.

The association of gap junctions with large particles in the crypt epithelium of the rat small intestine

Intercellular junctions in the epithelium of the rat small intestine were studied by the freeze-fracture method. Gap junctions were found between columnar cells of the crypt far more frequently than between absorptive cells of the villus. In addition, in the crypt, large particles 11 to 13 nm in diameter were often associated with the gap junction which primarily consisted of usual gap junctional particles 8 to 9 nm in diameter. Both the usual and large particles possessed a central pit. The intestinal crypt is the site of epithelial cell proliferation and differentiation in the process of physiological cell renewal. The predominant presence of gap junctions in this region suggests that they play a certain role in the proliferation and differentiation of crypt columnar cells. Further studies are required to elucidate the nature of the large particles, a precursor of typical connexons and/or a functionally different gap junction.

A reaction product from mercuric mercury, selenite and reduced glutathione

Reaction of mercuric mercury and selenite in the presence of reduced glutathione (GSH) was studied. A black complex containing GSH and equimolar amounts of mercury and selenium was obtained by the reaction of sodium selenite and mercuric chloride in the presence of excess amounts of GSH. This complex was soluble in water, but insoluble in ethanol. Toxicity of the complex was very low in comparison with mercuric chloride or sodium selenite. Formation of such complex of lower toxicity in animals as described above may play an important role in the modification of toxicity of mercuric mercury by selenite.