Elucidating the Biosynthesis of Chitin Filaments and their Configuration with Specific Proteins and Electron Microscopy

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Abstract

To deepen the knowledge of chitin synthesis, a yeast mutant has been used as a model. Purified chitin synthase I-containing vesicles (chitosomes) with a diameter of 85 to 120 nm are identified by electron microscopy to eject tiny fibers upon addition of UDP-N-acetylglucosamine. The filigree of extruded filaments fused gradually into a large three-dimensional network, which is degradable by a chitinase. The network is targeted and restructured by the Streptomyces chitin-binding protein CHB1, which has a very high affinity only for α-chitin. Within the chitosomes, filaments are found to be highly condensed within consecutive oval fibroids, which are specifically targeted by the α-chitin-binding protein. The presented data give new insights to the generation of chitin filaments with an antiparallel (α) configuration.

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