Dataset Information

Length Specificity and Polymerization Mechanism of (1,3)-?-d-Glucan Synthase in Fungal Cell Wall Biosynthesis.

ABSTRACT: (1,3)-?-d-Glucan synthase (GS) catalyzes formation of the linear (1,3)-?-d-glucan in the fungal cell wall and is a target of clinically approved antifungal antibiotics. The catalytic subunit of GS, FKS protein, does not exhibit significant sequence homology to other glycosyltransferases, and thus, significant ambiguity about its catalytic mechanism remains. One of the major technical barriers in studying GS is the absence of activity assay methods that allow characterization of the lengths and amounts of (1,3)-?-d-glucan due to its poor solubility in water and organic solvents. Here, we report a successful development of a novel GS activity assay based on size-exclusion chromatography coupled with pulsed amperometric detection and radiation counting (SEC-PAD-RC), which allows for the simultaneous characterization of the amount and length of the polymer product. The assay revealed that the purified yeast GS produces glucan with a length of 6550 ± 760 mer, consistent with the reported degree of polymerization of (1,3)-?-d-glucan isolated from intact cells. Pre-steady state kinetic analysis revealed a highly efficient but rate-determining chain elongation rate of 51.5 ± 9.8 s-1, which represents the first observation of chain elongation by a nucleotide-sugar-dependent polysaccharide synthase. Coupling the SEC-PAD-RC method with substrate analogue mechanistic probes provided the first unambiguous evidence that GS catalyzes non-reducing end polymerization. On the basis of these observations, we propose a detailed model for the catalytic mechanism of GS. The approaches described here can be used to determine the mechanism of catalysis of other polysaccharide synthases.

SUBMITTER: Chhetri A

PROVIDER: S-EPMC7015794 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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Length Specificity and Polymerization Mechanism of (1,3)-β-d-Glucan Synthase in Fungal Cell Wall Biosynthesis.

Chhetri Abhishek A Loksztejn Anna A Nguyen Hai H Pianalto Kaila M KM Kim Mi Jung MJ Hong Jiyong J Alspaugh J Andrew JA Yokoyama Kenichi K

Biochemistry 20200115 5

(1,3)-β-d-Glucan synthase (GS) catalyzes formation of the linear (1,3)-β-d-glucan in the fungal cell wall and is a target of clinically approved antifungal antibiotics. The catalytic subunit of GS, FKS protein, does not exhibit significant sequence homology to other glycosyltransferases, and thus, significant ambiguity about its catalytic mechanism remains. One of the major technical barriers in studying GS is the absence of activity assay methods that allow characterization of the lengths and a ...[more]

PMID: 31899625

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Dataset Information

Length Specificity and Polymerization Mechanism of (1,3)-?-d-Glucan Synthase in Fungal Cell Wall Biosynthesis.

Publications

Length Specificity and Polymerization Mechanism of (1,3)-β-d-Glucan Synthase in Fungal Cell Wall Biosynthesis.

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