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Abstract
When co-cultivated with chitin-containing fungi, Strepfomyces reticuli secretes the chitin-binding protein CHB2. Microscopical and immunological investigations revealed that CHBZ acts like a glue to mediate the contact between the fungal and the Streptomyces hyphae. CHBZ was purified to homogeneity, and the sequence of its N-terminal amino acids was determined and used to deduce an oligonucleotide, which was then used to probe a subgenomic library. The ch62 gene was cloned, sequenced and overexpressed. The deduced mature protein has a molecular mass of 18.6 kDa, and a large number of its amino acids are identical to those of CHBl from Streptomyces oliwaceowiridis. CHB2 effectively targets different types of α-chitin, but no other polysaccharide. The dissociation constant (Kd) for binding to purified crab shell chitin is 0 27 μM. Immunological studies suggest that homologues of CHBl and CHBZ are secreted by streptomycetes while growing in the presence of a-chitin-containing substrates.
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