The complex structure of polyhydroxybutyrate (PHB) granules: four orthologous and paralogous phasins occur in Ralstonia eutropha.
Analysis of the genome sequence of the polyhydroxyalkanoate- (PHA) accumulating bacterium Ralstonia eutropha strain H16 revealed three homologues (PhaP2, PhaP3 and PhaP4) of the phasin protein PhaP1. PhaP1 is known to constitute the major component of the layer at the surface of poly(3-hydroxybutyrate), poly(3HB), granules. PhaP2, PhaP3 and PhaP4 exhibited 42, 49 and 45 % identity or 61, 62 and 63 % similarity to PhaP1, respectively. The calculated molecular masses of PhaP1, PhaP2, PhaP3 and PhaP4 were 20.0, 20.2, 19.6 and 20.2 kDa, respectively. RT-PCR analysis showed that phaP2, phaP3 and phaP4 were transcribed under conditions permissive for accumulation of poly(3HB). 2D PAGE of the poly(3HB) granule proteome and analysis of the detected proteins by MALDI-TOF clearly demonstrated that PhaP1, PhaP3 and PhaP4 are bound to the poly(3HB) granules in the cells. PhaP3 was expressed at a significantly higher level in PhaP1-negative mutants. Occurrence of an unknown protein with an N-terminal amino-acid sequence identical to that of PhaP2 in crude cellular extracts of R. eutropha had previously been shown by others. Although PhaP2 could not be localized in vivo on poly(3HB) granules, in vitro experiments clearly demonstrated binding of PhaP2 to these granules. Further analysis of complete or partial genomes of other poly(3HB)-accumulating bacteria revealed the existence of multiple phasin homologues in Ralstonia solanacearum, Burkholderia fungorum and Azotobacter vinelandii. These new and unexpected findings should affect our current models of PHA-granule structure and may also have a considerable impact on the establishment of heterologous production systems for PHAs.
Pötter
Markus
M
Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Corrensstrasse 3, 48149 Münster, Germany.
Müller
Helena
H
Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Corrensstrasse 3, 48149 Münster, Germany.
Reinecke
Frank
F
Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Corrensstrasse 3, 48149 Münster, Germany.
Wieczorek
Roman
R
Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Corrensstrasse 3, 48149 Münster, Germany.
Fricke
Florian
F
Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen, Grisebachstrasse 8, 37077 Göttingen, Germany.|Genomik Netzwerk Göttingen, Georg-August-Universität Göttingen, Grisebachstrasse 8, 37077 Göttingen, Germany.
Bowien
Botho
B
Institut für Mikrobiologie und Genetik, Georg-August-Universität Göttingen, Grisebachstrasse 8, 37077 Göttingen, Germany.
Friedrich
Bärbel
B
Institut für Biologie, Humboldt-Universität Berlin, Chausseestrasse 117, 10115 Berlin, Germany.
Steinbüchel
Alexander
A
Institut für Molekulare Mikrobiologie und Biotechnologie, Westfälische Wilhelms-Universität Münster, Corrensstrasse 3, 48149 Münster, Germany.
D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D020118:Cupriavidus necator / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D006885:Hydroxybutyrates / Q000378:metabolism*; D002479:Inclusion Bodies / Q000737:chemistry* / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D011091:Polyesters / Q000378:metabolism*; D020543:Proteome; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic; D000094122:Polyhydroxybutyrates
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D006885:Hydroxybutyrates; D011091:Polyesters; D020543:Proteome; C118828:PHAP protein, Bacteria; C003182:poly-beta-hydroxybutyrate; D000094122:Polyhydroxybutyrates