Chitin and Yeast Budding

Keller, Frederick A.; Cabib, Enrico

doi:10.1016/s0021-9258(18)62098-8

Cited by 12 publications

(1 citation statement)

References 36 publications

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“…Mannoproteins appear to be synthesized in preference to chitin in an S. cerevisiae glucosamine auxotroph deprived of this amino sugar (Ballou et al, 1977), a priority that could result because the transferases involved in mannoprotein biosynthesis have a greater affinity for UDP-A-acetylglucosamine than does chitin synthetase. The K. lactis A-acetylglucosamine transferase, in fact, has a Km for UDP-A-acetylglucosamine that is 10-fold lower than the S. cerevisiae chitin synthetase Km (Keller & Cabib, 1971).…”

Section: Discussionmentioning

confidence: 95%

Purification of an .alpha.-N-acetylglucosaminyltransferase from the yeast Kluyveromyces lactis and a study of mutants defective in this enzyme activity

Douglas¹,

Ballou²

1982

Biochemistry

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An enzyme activity in Kluyveromyces lactis that catalyzes the transfer of N-acetylglucosamine from uridine diphosphate N-acetylglucosamine to alpha Man(1 leads to 3) alpha Man ( 1 leads to 2) alpha Man (1 leads to 2)Man to yield alpha Man(1 leads to 3) [alpha GlcNAc(1 leads to 2)] alpha Man(1 leads to 2) alpha Man (1 leads to 2)Man, a mannoprotein side-chain unit, has been solubilized by Triton X-100 and purified 18000-fold by a combination of ion-exchange chromatography, gel filtration, hydrophobic chromatography, and adsorption to a lectin column. The enzyme activity from a K. lactis mutant (mnn2-2) that made mannoprotein lacking N-acetylglucosamine in its side chains, but that possessed a normal level of transferase activity in cell extracts, was purified and compared with the enzyme from the wild-type strain. Both transferase activities are integral membrane proteins found in particles associated with endoplasmic reticulum. The two purified enzymes had the same apparent size, heat stability, Mn2+ requirement, and Km for donor and acceptor and a similar Vmax. Wild-type and mutant cells had similar pool sizes of sugar nucleotide donor, and they incorporated labeled N-acetylglucosamine into chitin at similar rates. No evidence was obtained for an inactive enzyme precursor in mutant cells that was activated upon breaking the cells, nor did the mutant cells contain a transferase inhibitor or a hexosaminidase that could remove the sugar from the mannoprotein during processing and secretion. The mnn2-2 locus appears to be allelic with a second mutant, mnn2-1, that has the same phenotype but that lacks transferase activity in cell extracts. This suggests that the two mutations affect the structural gene for the transferase, and we conclude that the mnn2-2 mutant could contain an altered enzyme that fails to function because it is improperly localized or oriented in the membrane.

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Section: Discussionmentioning

confidence: 95%

Purification of an .alpha.-N-acetylglucosaminyltransferase from the yeast Kluyveromyces lactis and a study of mutants defective in this enzyme activity

Douglas¹,

Ballou²

1982

Biochemistry

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Rapid reactions of spruce cells to elicitors released from the ectomycorrhizal fungus Hebeloma crustuliniforme, and inactivation of these elicitors by extracellular spruce cell enzymes

Salzer

Hebe

Reith

et al. 1996

Planta

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Abstract. Elicitors released from hyphae or cell walls of the ectomycorrhizal fungus Hebeloma crustuliniforme (Bull. ex Fries.) Qu~l. induced in suspension-cultured cells of Picea abies (L.) Karst. a set of fast reactions: (i) an immediate efflux of C1-into the medium, followed by a K § efflux; (ii) an influx of Ca 2 § (measured as accumulation of 45Ca2+ in the cells); (iii) a phosphorylation of a 63-kDa protein and dephosphorylation of a 65-kDa protein (detectable by 4 min after elicitor application); (iv) an alkalinization of the medium, and (v) a transient synthesis of H202. The removal of extracellular Ca 2 + by EGTA delayed the elicitor-induced alkalinization. A further reduction of this response could be achieved by TMB-8 an inhibitor of Ca 2 § release from intracellular stores. Moreover, the inhibition of protein kinase activity by staurosporine prevented the extracellular alkalinization completely. However, the effectiveness of the elicitors in inducing the extracellular alkalinization was strongly impaired by constitutively secreted enzymes of spruce cells which cleaved the elicitors to inactive fragments. It is suggested that in ectomycorrhizae the efficacy of elicitors released from fungal cell walls is controlled by apoplastic enzymes of the host; the plant itself is able to reduce the activity of fungal elicitors on their way through the plant cell wall. But those elicitors which finally reach the plasma membrane of host cells induce reactions that are similar to the early defense reactions in plant-pathogen interactions.

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Cleavage of chitinous elicitors from the ectomycorrhizal fungus Hebeloma crustuliniforme by host chitinases prevents induction of K + and Cl − release, extracellular alkalinization and H 2 O 2 synthesis of Picea abies cells

Salzer

Hebe

Hager

1997

Planta

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Rapid reactions comprising eux of K + and Cl A , phosphorylation of a 63-kDa protein (pp63), extracellular alkalinization and synthesis of H 2 O 2 are equally induced in cells of Picea abies (L.) Karst. by chitotetraose, colloidal chitin and cell wall elicitors from the ectomycorrhizal fungus Hebeloma crustuliniforme (Bull. ex Fries.) QueÂ l. an ectomycorrhizal partner of spruce. Cleavage of fungal cell wall elicitors and of arti®cial chitin elicitors to monomeric and dimeric fragments by apoplasmic spruce chitinases (36-kDa class I chitinase, pI 8.0, and 28-kDa chitinase, pI 8.7; EC 3.2.1.14) equally prevented induction of these rapid reactions. Also, N-acetylglucosamine oligomers and elicitors from the fungal cell walls showed a similar dependence of their activity on the degree of polymerisation. From these results it is suggested that, during ectomycorrhiza formation, only some of the chitin-derived elicitors reach their receptors at the plant plasma membrane, initiating reactions of the hypersensitive response in the host cells. The remaining fungal elicitors will be degraded to varying extents by wall-localized chitinases of the host root, reducing the defence reactions of the plant and allowing symbiotic interactions of both organisms. Abbreviations: DP = degree of polymerisation; HR = hypersensitive response; MS = mineral solution; Pi = inorganic phosphate; pp63 = phosphorylated protein of MW 63 kDa Correspondence to: P. Salzer; Fax

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Chitin and Yeast Budding

Cited by 12 publications

References 36 publications

Purification of an .alpha.-N-acetylglucosaminyltransferase from the yeast Kluyveromyces lactis and a study of mutants defective in this enzyme activity

Purification of an .alpha.-N-acetylglucosaminyltransferase from the yeast Kluyveromyces lactis and a study of mutants defective in this enzyme activity

Rapid reactions of spruce cells to elicitors released from the ectomycorrhizal fungus Hebeloma crustuliniforme, and inactivation of these elicitors by extracellular spruce cell enzymes

Cleavage of chitinous elicitors from the ectomycorrhizal fungus Hebeloma crustuliniforme by host chitinases prevents induction of K + and Cl − release, extracellular alkalinization and H 2 O 2 synthesis of Picea abies cells

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