A GTP-binding protein regulates the activity of (1-->3)-beta-glucan synthase, an enzyme directly involved in yeast cell wall morphogenesis.
Synthesis of (1-->3)-beta-D-glucan, the major structural component of the yeast cell wall, is synchronized with the budding cycle. Membrane-bound, GTP-stimulated (1-->3)-beta-glucan synthase was dissociated by stepwise treatment with salt and detergents into two soluble fractions, A and B, both required for activity. Fraction A was purified about 800-fold by chromatography on Mono Q and Sephacryl S-300 columns. During purification, GTP binding to protein correlated with synthase complementing activity. A 20-kDa GTP-binding protein was identified by photolabeling in the purified preparation. This preparation no longer required GTP for activity, but incubation with another fraction from the Mono Q column (A1) led to hydrolysis of bound GTP to GDP with a concomitant return of the GTP requirement. Thus, fraction A1 appears to contain a GTPase-activating protein. These results show that the GTP-binding protein not only regulates glucan synthase activity but can be regulated in turn, constituting a potential link between cell cycle controls and wall morphogenesis.
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Laboratory of Biochemistry and Metabolism, NIDDKD, National Institutes of Health, Bethesda, Maryland 20892.
Park
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Mullins
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JT
Cabib
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D001665:Binding Sites; D002473:Cell Wall / Q000201:enzymology; D019204:GTP-Binding Proteins / Q000502:physiology*; D005964:Glucosyltransferases / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006868:Hydrolysis; D008565:Membrane Proteins; D009024:Morphogenesis; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029702:Schizosaccharomyces pombe Proteins
D008565:Membrane Proteins; D029702:Schizosaccharomyces pombe Proteins; D006160:Guanosine Triphosphate; D005964:Glucosyltransferases; C020570:1,3-beta-glucan synthase; D019204:GTP-Binding Proteins