High molecular weight cyclic K K-1,4-glucan (referred to as cycloamylose) exhibited an artificial chaperone property toward three enzymes in different categories. The inclusion properties of cycloamylose effectively accommodated detergents, which keep the chemically denatured enzymes from aggregation, and promoted proper protein folding. Chemically denatured citrate synthase was refolded and completely recovered it's enzymatic activity after dilution with polyoxyethylenesorbitan buffer followed by cycloamylose treatment. The refolding was completed within 2 h, and the activity of the refolded citrate synthase was quite stable. Cycloamylose also promoted the refolding of denatured carbonic anhydrase B and denatured lysozyme of a reduced form. ß
The surface hydrophobicity of 12 strains of Bacillus spp. was examined in a hexadecane-aqueous partition system. Mature and germinated spores of Bacillus megaterium QM B1551 transferred to the hexadecane layer, while vegetative and sporulating cells did not. Wild-type spores were more hydrophobic than spores of an exosporium-deficient mutant of B. megaterium QM B1551, although the mutant spores were shown to be hydrophobic to some extent by using increased volumes of hexadecane. This result suggests that the exosporium is more hydrophobic than the spore coat and that the surface hydrophobicity of spores depends mainly on components of the exosporium. The surface hydrophobicity of spores of nine other species of Bacillus was also examined, and spores having an exosporium were more hydrophobic than those lacking an exosporium. Thus measurement of the hydrophobicity of spores by the hexadecane partition method may provide a simple and rapid preliminary means of determining the presence or absence of an exosporium.
Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a unique scavenger receptor that plays important roles in atherogenesis and has been thought to function as a monomer. Using coimmunoprecipitation studies, we demonstrate that human LOX-1 (hLOX-1) forms constitutive homo-interactions in vivo. Western blot analysis of cell lysates under nonreducing or reducing conditions revealed one clear immunoreactive species corresponding to the size of a putative receptor dimer or a monomer, respectively, consistent with the presence of disulfide-linked hLOX-1 complexes. Site-directed mutagenesis studies indicated that cysteine 140 has a key role in the formation of these disulfide-linked hLOX-1 dimers. Eliminating this intermolecular disulfide bond markedly impairs the recognition of Escherichia coli by hLOX-1. Furthermore, these dimers can act as a "structural unit" to form noncovalently associated oligomers, as demonstrated by a membrane-impermeant crosslinker, which resulted in immunoreactive species corresponding to the sizes of putative tetramers and hexamers. These results provide the first evidence for the existence of hLOX-1 dimers/oligomers.
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