title: Molecular uptake of chitooligosaccharides through chitoporin from the marine bacterium Vibrio harveyi.
abstract: BACKGROUND
  Chitin is the most abundant biopolymer in marine ecosystems. However, there is no accumulation of chitin in the ocean-floor sediments, since marine bacteria Vibrios are mainly responsible for a rapid turnover of chitin biomaterials. The catabolic pathway of chitin by Vibrios is a multi-step process that involves chitin attachment and degradation, followed by chitooligosaccharide uptake across the bacterial membranes, and catabolism of the transport products to fructose-6-phosphate, acetate and NH(3).
  
  
  RESULTS
  This study reports the isolation of the gene corresponding to an outer membrane chitoporin from the genome of Vibrio harveyi. This porin, expressed in E. coli, (so called VhChiP) was found to be a SDS-resistant, heat-sensitive trimer. Immunoblotting using anti-ChiP polyclonal antibody confirmed the expression of the recombinant ChiP, as well as endogenous expression of the native protein in the V. harveyi cells. The specific function of VhChiP was investigated using planar lipid membrane reconstitution technique. VhChiP nicely inserted into artificial membranes and formed stable, trimeric channels with average single conductance of 1.8±0.13 nS. Single channel recordings at microsecond-time resolution resolved translocation of chitooligosaccharides, with the greatest rate being observed for chitohexaose. Liposome swelling assays showed no permeation of other oligosaccharides, including maltose, sucrose, maltopentaose, maltohexaose and raffinose, indicating that VhChiP is a highly-specific channel for chitooligosaccharides.
  
  
  CONCLUSIONS
  We provide the first evidence that chitoporin from V. harveyi is a chitooligosaccharide specific channel. The results obtained from this study help to establish the fundamental role of VhChiP in the chitin catabolic cascade as the molecular gateway that Vibrios employ for chitooligosaccharide uptake for energy production.
authors: Biochemistry-Electrochemistry Research Unit, Schools of Chemistry and Biochemistry, Institute of Science, Suranaree University of Technology, Nakhon Ratchasima, Thailand. wipa@sut.ac.th
authors: Wipa
authors: W
authors: Suginta
authors: Watcharin
authors: W
authors: Chumjan
authors: Kozhinjampara R
authors: KR
authors: Mahendran
authors: Petra
authors: P
authors: Janning
authors: Albert
authors: A
authors: Schulte
authors: Mathias
authors: M
authors: Winterhalter
mesh_terms: D000595:Amino Acid Sequence; D059001:Aquatic Organisms / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002686:Chitin / Q000378:metabolism*; D003001:Cloning, Molecular; D015964:Gene Expression Regulation, Bacterial; D008081:Liposomes / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010539:Permeability; D017433:Protein Structure, Secondary; D021381:Protein Transport; D014733:Vibrio / Q000166:cytology / Q000235:genetics / Q000378:metabolism*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D008081:Liposomes; D002686:Chitin
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