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(1-->6)-beta-D-glucan as cell wall receptor for Pichia membranifaciens killer toxin
A Santos1, D Marquina, J A Leal
1Department of Microbiology, Biology Faculty, Complutense University of Madrid, Madrid 28040, Spain.
Abstract:
The killer toxin from Pichia membranifaciens CYC 1106, a yeast isolated from fermenting olive brines, binds primarily to the (1-->6)-beta-D-glucan of the cell wall of a sensitive yeast (Candida boidinii IGC 3430). The (1-->6)-beta-D-glucan was purified from cell walls of C. boidinii by alkali and hot-acetic acid extraction, a procedure which solubilizes glucans. The major fraction of receptor activity remained with the alkali-insoluble (1-->6)-beta- and (1-->3)-beta-D-glucans. The chemical (gas-liquid chromatography) and structural (periodate oxidation, infrared spectroscopy, and (1)H nuclear magnetic resonance) analyses of the fractions obtained showed that (1-->6)-beta-D-glucan was a receptor. Adsorption of most of the killer toxin to the (1-->6)-beta-D-glucan was complete within 2 min. Killer toxin adsorption to the linear (1-->6)-beta-D-glucan, pustulan, and a glucan from Penicillium allahabadense was observed. Other polysaccharides with different linkages failed to bind the killer toxin. The specificity of the killer toxin for its primary receptor provides an effective means to purify the killer toxin, which may have industrial applications for fermentations in which salt is present as an adjunct, such as olive brines. This toxin shows its maximum killer activity in the presence of NaCl. This report is the first to identify the (1-->6)-beta-D-glucan as a receptor for this novel toxin.
Insights
A novel killer toxin from Pichia membranifaciens yeast specifically binds to (1-->6)-beta-D-glucan, a component of sensitive yeast cell walls. This discovery enables toxin purification and suggests industrial applications in salt-containing fermentations.
Area of Science:
- Microbiology and Biochemistry
- Yeast genetics and physiology
- Molecular interactions and binding specificity
Background:
- Pichia membranifaciens produces a killer toxin with potential industrial applications.
- Understanding toxin-receptor interactions is crucial for harnessing its capabilities.
- Previous research has not identified the specific receptor for this novel toxin.
Purpose of the Study:
- To identify the primary receptor for the killer toxin produced by Pichia membranifaciens CYC 1106.
- To characterize the binding properties and specificity of the killer toxin.
- To explore potential industrial applications of the toxin and its receptor.
Main Methods:
- Purification of (1-->6)-beta-D-glucan from Candida boidinii cell walls using alkali and hot-acetic acid extraction.
- Chemical analyses including gas-liquid chromatography, periodate oxidation, infrared spectroscopy, and 1H nuclear magnetic resonance.
- Toxin adsorption assays with various glucans and polysaccharides to determine binding specificity.
Main Results:
- The primary receptor for the killer toxin was identified as (1-->6)-beta-D-glucan.
- Complete toxin adsorption to (1-->6)-beta-D-glucan occurred within 2 minutes.
- The toxin specifically bound to linear (1-->6)-beta-D-glucans, including pustulan, but not other polysaccharides.
Conclusions:
- The (1-->6)-beta-D-glucan is confirmed as the specific receptor for the Pichia membranifaciens killer toxin.
- This specific binding allows for effective purification of the killer toxin.
- The toxin's activity is enhanced by NaCl, suggesting applications in industrial fermentations involving salt.