Presence of methyl sterol and bacteriohopanepolyol in an outer-membrane preparation from Methylococcus capsulatus  (Bath).
Cytoplasmic/intracytoplasmic and outer membrane preparations of Methylococcus capsulatus (Bath) were isolated by sucrose density gradient centrifugation of a total membrane fraction prepared by disruption using a French pressure cell.  The cytoplasmic and/or intracytoplasmic membrane fraction consisted of two distinct bands, Ia and Ib (buoyant densities 1.16 and 1.8 g ml-1, respectively) that together contained 57% of the protein, 68% of the phospholipid, 73% of the ubiquinone and 89% of the CN-sensitive NADH oxidase activity.  The only apparent difference between these two cytoplasmic bands was a much higher phospholipid content for Ia.  The outer membrane fraction (buoyant density 1.23 - 1.24 g ml-1) contained 60% of the lipopolysaccharide-associated, beta-hydroxypalmitic acid, 74% of the methylsterol, and 66% of the bacteriohopanepolyol (BHP); phospholipid to methyl sterol or BHP ratios were 6:1.  Methanol dehydrogenase activity and a c-type cytochrome were also present in this outer membrane fraction.  Phospholipase A activity was present in both the cytoplasmic membrane and outer membrane fractions.  The unique distribution of cyclic triterpenes may reflect a specific role in conferring outer membrane stability in this methanotrophic bacterium.
Jahnke
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NASA-Ames Research Center, Moffett Field, California 94035, USA.
Stan-Lotter
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Kato
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Hochstein
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D005075:Biological Evolution; D002462:Cell Membrane / Q000737:chemistry* / Q000201:enzymology / Q000648:ultrastructure; D002499:Centrifugation, Density Gradient; D008563:Membrane Lipids / Q000032:analysis*; D008565:Membrane Proteins / Q000032:analysis / Q000378:metabolism; D008772:Methylococcaceae / Q000201:enzymology / Q000502:physiology / Q000648:ultrastructure*; D008854:Microscopy, Electron; D010740:Phospholipases / Q000378:metabolism; D010741:Phospholipases A / Q000378:metabolism; D010743:Phospholipids / Q000032:analysis; D013261:Sterols / Q000032:analysis* / Q000378:metabolism; D014315:Triterpenes / Q000032:analysis*
D008563:Membrane Lipids; D008565:Membrane Proteins; D010743:Phospholipids; D013261:Sterols; D014315:Triterpenes; D010740:Phospholipases; D010741:Phospholipases A