title: Molecular characterization of the modular chitin binding protein Cbp50 from Bacillus thuringiensis serovar konkukian.
abstract: Bacillus thuringiensis is an insecticidal bacterium whose chitinolytic system may be exploited to improve the insecticidal system of Bt-crops. A nucleotide fragment of 1368 bp from B. thuringiensis serovar konkukian S4, containing the complete coding sequence of the chitin binding protein Cbp50, was cloned and sequenced. Analyses have shown the protein to contain a modular structure consisting of an N-terminal CBM33 domain, two copies of a fibronectin-like domain and a C-terminal chitin binding domain classified as CBM5. The Cbp50 protein was heterologously expressed in Escherichia coli, purified and assessed for chitin binding activity. A deletion mutant (CBD-N; containing only the N-terminal CBM33 domain) of Cbp50 was produced to determine the role of C-terminal domains in the binding activity of the protein. The full-length Cbp50 was shown to bind β-chitin most efficiently followed by α-chitin, colloidal chitin and cellulose. The polysaccharide binding activity of CBD-N was drastically decreased. The data demonstrate that both the N-terminal and C-terminal domains of Cbp50 are essential for the efficient binding of chitin. The purified Cbp50 showed antifungal activity against the phytopathogenic fungus Fusarium oxysporum and the opportunistic human pathogen Aspergillus niger. This is the first report of a modular chitin binding protein in bacteria.
authors.affiliation: National Institute for Biotechnology & Genetic Engineering, Faisalabad, Pakistan.
authors.forename: Muhammad Aamer
authors.initials: MA
authors.lastname: Mehmood
authors.forename: Xiang
authors.initials: X
authors.lastname: Xiao
authors.forename: Fauzia Yusuf
authors.initials: FY
authors.lastname: Hafeez
authors.forename: Yingbao
authors.initials: Y
authors.lastname: Gai
authors.forename: Fengping
authors.initials: F
authors.lastname: Wang
mesh_terms: D000595:Amino Acid Sequence; D000935:Antifungal Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D001228:Aspergillosis / Q000382:microbiology; D001234:Aspergillus niger / Q000187:drug effects / Q000254:growth & development; D001413:Bacillus thuringiensis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism* / Q000494:pharmacology; D001483:Base Sequence; D002686:Chitin / Q000378:metabolism*; D060585:Fusariosis / Q000382:microbiology; D005670:Fusarium / Q000187:drug effects / Q000254:growth & development; D006801:Humans; D008969:Molecular Sequence Data; D011485:Protein Binding; D017434:Protein Structure, Tertiary
chemical_list: D000935:Antifungal Agents; D001426:Bacterial Proteins; D002686:Chitin