Abstract
The ultrastructure and polypeptide composition of a novel membrane junction in magnesium-starved Escherichia coli are described in this report. Freeze-fracture replicas reveal the junction as a site-specific membrane particle array with four fracture faces. Each junction consists of a cell membrane, a midline zone and a coupled membrane. Membrane particles associated with the junction extend from the hydrophobic region of the cell membrane across the hydrophilic midline zone and into the hydrophobic region of the coupled membrane. After negative staining or after rotary shadowing of freeze-fractured specimens, these particles were seen to consist of two similar but slightly offset bracket-shaped subunits separated by a small space. Optical analysis confirms this structure. Since the apposing membranes are bracketed or linked by their component particles, the name "bracket junction" is proposed for the complex. Methods are described for isolating a membrane fraction enriched in these junctional complexes; the fraction contains a prominent glycoprotein (mol wt 90,000) as well as a number of other components. The bracket junction is compared with the vertebrate gap junction in terms of both structure and possible roles in facilitating the permeation of the cell by small molecules.
Full Text
The Full Text of this article is available as a PDF (5.2 MB).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- BROCK T. D. Effects of magnesium ion deficiency on Escherichia coli and possible relation to the mode of action of novobiocin. J Bacteriol. 1962 Oct;84:679–682. doi: 10.1128/jb.84.4.679-682.1962. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bayer M. E. Areas of adhesion between wall and membrane of Escherichia coli. J Gen Microbiol. 1968 Oct;53(3):395–404. doi: 10.1099/00221287-53-3-395. [DOI] [PubMed] [Google Scholar]
- Fairbanks G., Steck T. L., Wallach D. F. Electrophoretic analysis of the major polypeptides of the human erythrocyte membrane. Biochemistry. 1971 Jun 22;10(13):2606–2617. doi: 10.1021/bi00789a030. [DOI] [PubMed] [Google Scholar]
- Fiil A., Branton D. Changes in the plasma membrane of Escherichia coli during magnesium starvation. J Bacteriol. 1969 Jun;98(3):1320–1327. doi: 10.1128/jb.98.3.1320-1327.1969. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Goodenough D. A., Revel J. P. A fine structural analysis of intercellular junctions in the mouse liver. J Cell Biol. 1970 May;45(2):272–290. doi: 10.1083/jcb.45.2.272. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Johnson R., Hammer M., Sheridan J., Revel J. P. Gap junction formation between reaggregated Novikoff hepatoma cells. Proc Natl Acad Sci U S A. 1974 Nov;71(11):4536–4540. doi: 10.1073/pnas.71.11.4536. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Loewenstein W. R. Permeability of membrane junctions. Ann N Y Acad Sci. 1966 Jul 14;137(2):441–472. doi: 10.1111/j.1749-6632.1966.tb50175.x. [DOI] [PubMed] [Google Scholar]
- Morgan C., Rosenkranz H. S., Chan B., Rose H. M. Electron microscopy of magnesium-depleted bacteria. J Bacteriol. 1966 Feb;91(2):891–895. doi: 10.1128/jb.91.2.891-895.1966. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Pinto da Silva P., Branton D. Membrane splitting in freeze-ethching. Covalently bound ferritin as a membrane marker. J Cell Biol. 1970 Jun;45(3):598–605. doi: 10.1083/jcb.45.3.598. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Pinto da Silva P. Translational mobility of the membrane intercalated particles of human erythrocyte ghosts. pH-dependent, reversible aggregation. J Cell Biol. 1972 Jun;53(3):777–787. doi: 10.1083/jcb.53.3.777. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Saito A., Smigel M., Fleischer S. Membrane junctions in the intermembrane space of mitochondria from mammalian tissues. J Cell Biol. 1974 Mar;60(3):653–663. doi: 10.1083/jcb.60.3.653. [DOI] [PMC free article] [PubMed] [Google Scholar]