151. Li L., Drake, Jr. R. R. , Clement S., and R. M. Brown, Jr. 1993. ß-glucan synthesis in the cotton fiber. III. Identification of UDP-glucose-binding components of ß-glucan synthases by photoaffinity labeling with [ß-32P]-5'N3-UDP-glucose. Plant Physiol. 101: 1149-1156.
Using differential product entrapment and photolabeling under specifying conditions, we identified a 37-kD polypeptide as the best candidate among the UDP-glucose-binding polypeptides for the catalytic subunit of cotton (Gossypium hirsutum) cellulose synthase. This polypeptide is enriched by entrapment under conditions favoring ß-1,4-glucan synthesis, and it is magnesium dependent and sensitive to unlabeled UDP-glucose. A 52-kD polypeptide was identified as the most likely candidate for the catalytic subunit of ß-1,3-glucan synthase because this polypeptide is the most abundant protein in the entrapment fraction obtained under conditions favoring ß-1,3-glucan synthesis, is coincident with ß-1,3-glucan synthase activity, and is calcium-dependent. The possible involvement of other peptides in the synthesis of ß-1,3-glucan is discussed.
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