PMID:10692361

Citation	Grahn, AM, Haase, J, Bamford, DH and Lanka, E (2000) Components of the RP4 conjugative transfer apparatus form an envelope structure bridging inner and outer membranes of donor cells: implications for related macromolecule transport systems. J. Bacteriol. 182:1564-74
Abstract	During bacterial conjugation, the single-stranded DNA molecule is transferred through the cell envelopes of the donor and the recipient cell. A membrane-spanning transfer apparatus encoded by conjugative plasmids has been proposed to facilitate protein and DNA transport. For the IncPalpha plasmid RP4, a thorough sequence analysis of the gene products of the transfer regions Tra1 and Tra2 revealed typical features of mainly inner membrane proteins. We localized essential RP4 transfer functions to Escherichia coli cell fractions by immunological detection with specific polyclonal antisera. Each of the gene products of the RP4 mating pair formation (Mpf) system, specified by the Tra2 core region and by traF of the Tra1 region, was found in the outer membrane fraction with one exception, the TrbB protein, which behaved like a soluble protein. The membrane preparation from Mpf-containing cells had an additional membrane fraction whose density was intermediate between those of the cytoplasmic and outer membranes, suggesting the presence of attachment zones between the two E. coli membranes. The Tra1 region is known to encode the components of the RP4 relaxosome. Several gene products of this transfer region, including the relaxase TraI, were detected in the soluble fraction, but also in the inner membrane fraction. This indicates that the nucleoprotein complex is associated with and/or assembled facing the cytoplasmic site of the E. coli cell envelope. The Tra1 protein TraG was predominantly localized to the cytoplasmic membrane, supporting its potential role as an interface between the RP4 Mpf system and the relaxosome.
Links	PubMed PMC94453
Keywords	Bacterial Proteins/chemistry; Bacterial Proteins/metabolism; Biological Transport; Cell Fractionation; Cell Membrane/metabolism; Conjugation, Genetic; DNA Replication; Escherichia coli/genetics; Escherichia coli/metabolism; Membrane Proteins/chemistry; Membrane Proteins/metabolism; Microscopy, Electron; Periplasm/metabolism; Plasmids/genetics; Replication Origin
edit table

Annotations

Gene product	Qualifier	GO Term	Evidence Code	with/from	Aspect	Extension	Notes	Status
9ZZZZ:Q03534		GO:0042597: periplasmic space	ECO:0000314: direct assay evidence used in manual assertion		C		Fig. 5. Cells containing a transfer plasmid were subjected to EDTA-lysozyme treatment in order to release periplasmic proteins. Anti-TrbJ antibodies were used to identify TrbJ as belonging to the periplasmic space.	complete
9ZZZZ:Q52363		GO:0005886: plasma membrane	ECO:0000314:		C		Figure 2A (isopycnic gradient centrifugation + western blot) shows that TrbE is found in the outer membrane (OM) and the cytoplasmic membrane (CM) portions.	complete
9ZZZZ:Q52363		GO:0019867: outer membrane	ECO:0000314:		C		Figure 2A (isopycnic gradient centrifugation + western blot) shows that TrbE is found in the outer membrane (OM) and the cytoplasmic membrane (CM) portions.	complete
ECO24:SELA		GO:0043952: protein transport by the Sec complex	ECO:0000315:		P		Figure 7 demonstrates the protein transfer complex which contains the Sec complex.	complete
ECOLI:TRAG1		GO:0005886: plasma membrane	ECO:0000314:		C		Figure 2B. The membrane portion of the cell was isolated by centrifugation, and the outer membrane and inner membrane were separated by isopycnic sucrose density gradient centrifugation of the total membrane fraction. Anti-TraG antibodies were raised in rabbit. Fig. 2B clearly shows that TraG is localized to the inner membrane. Note: "bacterial inner membrane" is a narrow synonym of the GO term "plasma membrane," so the GO term is correct.	complete

References

See Help:References for how to manage references in GONUTS.