ANALYSIS OF XYSA, A GENE FROM STREPTOMYCES-HALSTEDII JM8 THAT ENCODESA 45-KILODALTON MODULAR XYLANASE, XYS1

The gene xysA from Streptomyces halstedii JM8 encodes a protein of 461 amino acids (Xys1) which is secreted into the culture supernatant as a protein of 45 kDa (Xys1L). Later, this form is proteolytically proce ssed after residue D-362 to produce the protein Xys1S, which conserves the same xylanolytic activity. The cleavage removes a domain of 99 am ino acids that shows similarity to bacterial cellulose binding domains and that allows the protein Xys1L to bind to crystalline cellulose (A vicel). Expression of this monocistronic gene is affected by the carbo n source present in the culture medium, xylan being the best inducer. By using an anti-Xys1L serum, we have been able to detect xylanases si milar in size to Xys1L and Xys1S in most of the different Streptomyces species analyzed, suggesting the ubiquity of these types of xylanases and their processing mechanism.