A Development-Specific Ca2+-Binding Protein from Myxococcus Xanthus
Myxococcus xanthus is a Gram-negative soil bacterium that undergoes a unique developmental cycle (for reviews see Rosenberg 1984). When starved for nutrients on a solid surface, the cells utilize their gliding motility to aggregate and form mounds called fruiting bodies. Some of the rod-shaped cells then differentiate into round or ovoid myxospores, which are resistant to heat, desiccation, UV irradiation, and sonication. During development there are many changes in the pattern of protein synthesis, the most striking of which is the appearance of protein S (Inouye et al. 1979a,b). Synthesis of protein S is induced early in development and increases until it reaches 15% of total protein synthesis at the stage of mound formation. It accumulates in the cytoplasm as a soluble protein until the onset of sporulation, after which most of it is found assembled on the surface of the myxospores (Inouye et al. 1979b) and a smaller amount inside the spores (Teintze et al. 1985a,b). Protein S can be removed from the surface of the spores by extraction with 1 N NaCl or 10 mM EDTA or 10 mM EGTA and can be reassembled on the spores by adding a 10 mM excess of Ca2+ ion or removing the NaCl by dialysis (Inouye et al. 1979b). Protein S is an acidic (pI 4.5), heat-stable protein of 173 amino acid residues and a molecular weight of 18792, with a very high content of ß-structure (Inouye et al. 1981, 1983a); it crystallizes differently in the presence and absence of Ca2+ (Inouye et al. 1980).
KeywordsAgar Codon EDTA Agarose Cysteine
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