title: Effect of over-expression of phasin gene from Aeromonas hydrophila on biosynthesis of copolyesters of 3-hydroxybutyrate and 3-hydroxyhexanoate.
abstract: The gene phaPAh, encoding the protein phasin that is associated with poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) granule of Aeromonas hydrophila 4AK4, was cloned and characterized. Recombinant strains harboring additional copies of the phasin gene (phaPAh) and the polyhydroxyalkanoate (PHA) synthase gene (phaCAh) accumulated PHBHHx copolyesters consisting of 21 mol% 3-hydroxyhexanoate (3HHx) as compared to 14 mol% 3HHx produced by wild type strain. The molecular weight of PHBHHx produced by the above recombinants was lower than that obtained from the wild type strain grown under similar conditions. Over-expression of phaPAh led to the production of more PHA granules but with reduced sizes. SDS-PAGE showed that PhaPAh was the predominant protein present in the PHBHHx granules. The RT-PCR results suggested that phasin PhaPAh, regulated phaCAh gene at the transcription level. Gene PhaPWe from Wautersia eutropha (formerly Ralstonia eutropha; encoding a 20 kDa protein with low amino acid homology to the A. hydrophila 13 kDa protein) cloned into A. hydrophila 4AK4 exhibited similar effects on PHBHHx production and PHBHHx composition. These data suggest that the phasins could represent a protein family possessing similar functions but different structures.
authors.affiliation: MOE Laboratory of Protein Science, Department of Biological Science and Biotechnology, Tsinghua University, Beijing 100084, PR China.
authors.forename: Shu-Jun
authors.initials: SJ
authors.lastname: Tian
authors.forename: Wei-Jian
authors.initials: WJ
authors.lastname: Lai
authors.forename: Zhong
authors.initials: Z
authors.lastname: Zheng
authors.forename: He-Xiang
authors.initials: HX
authors.lastname: Wang
authors.forename: Guo-Qiang
authors.initials: GQ
authors.lastname: Chen
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000378:metabolism; D016980:Aeromonas hydrophila / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D002208:Caproates / Q000378:metabolism; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D015870:Gene Expression; D005798:Genes, Bacterial; D008854:Microscopy, Electron; D011091:Polyesters / Q000378:metabolism*; D016133:Polymerase Chain Reaction
chemical_list: D001426:Bacterial Proteins; D002208:Caproates; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C118828:PHAP protein, Bacteria; D011091:Polyesters; C045051:3-hydroxyhexanoic acid; D020155:3-Hydroxybutyric Acid