Translocation domain: Difference between revisions

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[[Image: Colicin Translocation.png|500px|thumb| A diagram showing a generalised translocation path of the colicins from group A and group B into the cytoplasm, not showing all types of cytotoxic activity<ref> PMID: 21060316</ref>]]

Colicins that recruit the proteins from the Tol system are classed as being group A colicins, and those using the Ton system are group B colicins. Group A colicins also recruit a co-receptor to aid their translocation, such as [[OmpF]] or [[Tol C]]<ref> PMID: 6281233 </ref>, which is not something also seen in Group B colicins<ref> PMID: 17347522 </ref>. They may indiscriminately recruit other membrane proteins to aid translocation, that have transient interaction - this would explain why they have not yet been identified.

Colicins that recruit the proteins from the Tol system are classed as being group A colicins, and those using the Ton system are group B colicins. Group A colicins also recruit a co-receptor to aid their translocation, such as [[OmpF]] or [[Tol C]]<ref> PMID: 6281233 </ref>, which is not something also seen in Group B colicins<ref> PMID: 17347522 </ref>. They may indiscriminately recruit other membrane proteins to aid translocation, that have transient interaction - this would explain why they have not yet been identified. The two systems, tol and ton, import the proteins through two distinct mechanisms.

Once they have bound to the receptor and recruited translocation proteins, many colicins are known to unfold before moving across the membrane into the cytoplasm. However, the diameter of the unfolded peptide exceeds the diameter of the pores formed by the proteins recruited into the area<ref> PMID: 1537329 </ref><ref> PMID: 1380671 </ref>.

==Group A colicins==

All except for [[Colicin N]] require two outer membrane proteins, both a receptor, such as [[BtuB]], and a co-receptor, such as OmpF or TolC. One proposed model for the translocation across the outer membrane is this<ref> PMID: 17347522 </ref>:

The outer membrane receptor binds to the colicin, and the co-receptor is recruited and interacts with the T domain of the colicin<275>. The T domain passes through the pore formed by the co-receptor and recruits the Tol proteins<417>. The C domain of the colicin enters the periplasm, probably through a separate co-receptor<698>.

The T domain then directs transit across the periplasm of the C domain. The C domain is what is required of the colicin for the killing of the cell, and is sufficient to kill the cell without the other domains once it is inside.

==Group B colicins==

All except for [[Colicin 5]] and [[Colicin 10]] use a single outer membrane protein for both binding and transport of the T domain into the periplasm, such as the [[Cir]] protein. A proposed translocation mechanism of the colicin is<ref> PMID: 17347522 </ref>:

Colicin binding to the outer membrane protein promotes an interaction between the outer membrane protein, and [[TonB]] in the periplasm. Energy from the PMF may open a pore in the outer membrane protein by removal of the plug domain of the protein, and allowing the T domain of the colicin to enter into the periplasm. Once inside, the T domain and TonB interact to allow entry of the cytotoxic domain.

Crucial for the interaction between the colicin and TonB is the TonB box, a conserved sequence found in the T domain of the colicin. More than one may be present.

==References==

Translocation domain: Difference between revisions

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@@ Line 3: / Line 3: @@
 [[Image: Colicin Translocation.png|500px|thumb| A diagram showing a generalised translocation path of the colicins from group A and group B into the cytoplasm, not showing all types of cytotoxic activity<ref> PMID: 21060316</ref>]]
-Colicins that recruit the proteins from the Tol system are classed as being group A colicins, and those using the Ton system are group B colicins. Group A colicins also recruit a co-receptor to aid their translocation, such as [[OmpF]] or [[Tol C]]<ref> PMID: 6281233 </ref>, which is not something also seen in Group B colicins<ref> PMID: 17347522 </ref>. They may indiscriminately recruit other membrane proteins to aid translocation, that have transient interaction - this would explain why they have not yet been identified.
+Colicins that recruit the proteins from the Tol system are classed as being group A colicins, and those using the Ton system are group B colicins. Group A colicins also recruit a co-receptor to aid their translocation, such as [[OmpF]] or [[Tol C]]<ref> PMID: 6281233 </ref>, which is not something also seen in Group B colicins<ref> PMID: 17347522 </ref>. They may indiscriminately recruit other membrane proteins to aid translocation, that have transient interaction - this would explain why they have not yet been identified. The two systems, tol and ton, import the proteins through two distinct mechanisms.
 Once they have bound to the receptor and recruited translocation proteins, many colicins are known to unfold before moving across the membrane into the cytoplasm. However, the diameter of the unfolded peptide exceeds the diameter of the pores formed by the proteins recruited into the area<ref> PMID: 1537329 </ref><ref> PMID: 1380671 </ref>.
+==Group A colicins==
+All except for [[Colicin N]] require two outer membrane proteins, both a receptor, such as [[BtuB]], and a co-receptor, such as OmpF or TolC. One proposed model for the translocation across the outer membrane is this<ref> PMID: 17347522 </ref>:
+The outer membrane receptor binds to the colicin, and the co-receptor is recruited and interacts with the T domain of the colicin<275>. The T domain passes through the pore formed by the co-receptor and recruits the Tol proteins<417>. The C domain of the colicin enters the periplasm, probably through a separate co-receptor<698>.
+The T domain then directs transit across the periplasm of the C domain. The C domain is what is required of the colicin for the killing of the cell, and is sufficient to kill the cell without the other domains once it is inside.
+==Group B colicins==
+All except for [[Colicin 5]] and [[Colicin 10]] use a single outer membrane protein for both binding and transport of the T domain into the periplasm, such as the [[Cir]] protein. A proposed translocation mechanism of the colicin is<ref> PMID: 17347522 </ref>:
+Colicin binding to the outer membrane protein promotes an interaction between the outer membrane protein, and [[TonB]] in the periplasm. Energy from the PMF may open a pore in the outer membrane protein by removal of the plug domain of the protein, and allowing the T domain of the colicin to enter into the periplasm. Once inside, the T domain and TonB interact to allow entry of the cytotoxic domain.
+Crucial for the interaction between the colicin and TonB is the TonB box, a conserved sequence found in the T domain of the colicin. More than one may be present.
 ==References==
 <references/>