Characteristics and Function of the Chitin Binding Protein from Xenorhabdus nematophila.

Genome sequence analysis (GenBank access No.: FN667742.1) shows that Xenorhabdus nematophila ATCC19061 contains one gene encoding chitin binding protein (Xn-CBP). In order to study the characteristics and function of Xn-CBP, the 600 bp Xn-cbp gene was cloned and sequenced from X. nematophila HB310. Sequence analyses showed that the Xn-cbp gene encoded 199 amino acids with a calculated mass of 28 kDa and an isoelectric point of 8.00. Xn-CBP contained a signal peptide and a chitin binding domain. Xn-CBP was expressed with histidine tags in Escherichia coli BL21 (DE3) and purified. The Bmax and Kd values were 2.46 and 4.08, respectively, for Xn-CBP to colloidal chitin, which were stronger than that of α-chitin and β-chitin. Xn-CBP had insecticidal activity against the second instar larvae of Helicoverpa armigera with a growth inhibition rate of 84.08% and a corrected mortality rate of 2.78%. Xn-CBP had an antifungal effect on Coniothyrium diplodiella, Verticillium dahlia, and Fusarium oxysporum. The highest spore germination inhibitory effect occurred on C. diplodiella with the inhibition rate of 83.11%. The hyphal growth inhibition rate to F. oxysporum, 41.52%, was higher than other fungi.