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Cell wall deficiency in slime strains of Neurospora crassa: osmotic inhibition of cell wall synthesis and Beta-D-glucan synthase activity
Braz. j. med. biol. res ; 27(12): 2843-57, Dec. 1994. tab, graf
Article in English | LILACS | ID: lil-153283
ABSTRACT
1. The RCP-3 S/H mutant of Neurospora crassa was obtained by vegetative selection in medium of high osmolarity of a mycelial form an fz, sg, os-1 ("smile"-like) segregant. The mutant exhibits spheroplast-hyphal dimorphism conditioned by the osmolarity of the culture medium (pietro et al. (1990). Journal of General Microbiology, 136 121-129). The carbohydrate composition of the cell wall of the mutant was different from that of the wild type in the absence of an alkalisoluble galactosaminoglycan polymer. Furthermore the mutant cell wall had a somewhat lower content of ß-glucan relative to that of chitin. 2. Increasing concentrations of sorbitol in the culture medium of the mutant inhibited by 10-fold the formation of cell wall relative to toal biomass. The cell wall of the mutant cultured in the presence of sorbitol lacked mannose-and galactose-containing polymers, and also showed progressively lower amounts of ß-glucan relative to chitin. 3. The activity of membrane-bound (1-3)-ß-D-glucan synthase from the mutant grown in the absence of sorbitol shared several properties with the wil type enzyme (i.e., Km app, Vmax, stability at 30ºC, activation by GTPyS, and dissociability by treatment with NaCl and Tergitol NP-40 into a membrane-bound catalytic center and GTP-binding activating protein). On the other hand, the enzyme from the mutant but not that from the wild type was inactivated by about 15 per cent by treatment with NaCl and detergent. 4. At high concentrations of sorbitol (1.0M) the RCP-3 S/H mutant exclusively produced spheroplasts devoid of (1-3)-ß-D-glucan synthase activity. The defect was at the level of the membrane-bound catalytic center. The activity of the GTP-binding activating factor was apparently normal in these cells. 5. These results suggest that the definitive loss of cell wall in the N. crassa "slime" RCP-3 S/H mutant was due to a defect in (1-3)-ß-D-glucan synthase activity which wass exaggerated in the presence of high osmolyte concentrations
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Index: LILACS (Americas) Main subject: Sorbitol / Cell Wall / Glucose / Glucosyltransferases / Guanosine Triphosphate / Neurospora crassa Language: English Journal: Braz. j. med. biol. res Journal subject: Biology / Medicine Year: 1994 Type: Article

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Index: LILACS (Americas) Main subject: Sorbitol / Cell Wall / Glucose / Glucosyltransferases / Guanosine Triphosphate / Neurospora crassa Language: English Journal: Braz. j. med. biol. res Journal subject: Biology / Medicine Year: 1994 Type: Article