Editing Cooperative binding (section)

=== Transcription factors ===
Cooperative binding of proteins onto nucleic acids has also been shown. A classical example is the binding of the [[lambda phage]] repressor to its operators, which occurs cooperatively.<ref name=Ptashne1980>{{cite journal | vauthors = Ptashne M, Jeffrey A, Johnson AD, Maurer R, Meyer BJ, Pabo CO, Roberts TM, Sauer RT | title = How the lambda repressor and cro work | journal = Cell | volume = 19 | issue = 1 | pages = 1–11 | date = January 1980 | pmid = 6444544 | doi = 10.1016/0092-8674(80)90383-9 | s2cid = 54281357 }}</ref><ref name=Ackers1982>{{cite journal | vauthors = Ackers GK, Johnson AD, Shea MA | title = Quantitative model for gene regulation by lambda phage repressor | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 79 | issue = 4 | pages = 1129–33 | date = February 1982 | pmid = 6461856 | pmc = 345914 | doi = 10.1073/pnas.79.4.1129 | bibcode = 1982PNAS...79.1129A | doi-access = free }}</ref> Other examples of transcription factors exhibit positive cooperativity when binding their target, such as the repressor of the TtgABC pumps<ref name=Krell2007>{{cite journal | vauthors = Krell T, Terán W, Mayorga OL, Rivas G, Jiménez M, Daniels C, Molina-Henares AJ, Martínez-Bueno M, Gallegos MT, Ramos JL | title = Optimization of the palindromic order of the TtgR operator enhances binding cooperativity | journal = Journal of Molecular Biology | volume = 369 | issue = 5 | pages = 1188–99 | date = June 2007 | pmid = 17498746 | doi = 10.1016/j.jmb.2007.04.025 }}</ref> (n=1.6), as well as conditional cooperativity exhibited by the transcription factors [[HOXA11]] and [[FOXO1]].<ref name="Nnamani-et-al-2016">{{cite journal | last1=Nnamani | first1=Mauris C. | display-authors=etal | year=2016 | title=A derived allosteric switch underlies the evolution of conditional cooperativity between HOXA11 and FOXO1 | journal=Cell Reports | volume=15 | issue=10| pages=2097–2108 | doi=10.1016/j.celrep.2016.04.088| pmid=27239043 | doi-access=free | hdl=2437/230273 | hdl-access=free }}</ref>

Conversely, examples of negative cooperativity for the binding of transcription factors were also documented, as for the homodimeric repressor of the ''[[Pseudomonas putida]]'' [[cytochrome P450]]cam hydroxylase operon<ref name=Arakami2011>{{cite journal | vauthors = Aramaki H, Kabata H, Takeda S, Itou H, Nakayama H, Shimamoto N | title = Formation of repressor-inducer-operator ternary complex: negative cooperativity of d-camphor binding to CamR | journal = Genes to Cells | volume = 16 | issue = 12 | pages = 1200–7 | date = December 2011 | pmid = 22093184 | doi = 10.1111/j.1365-2443.2011.01563.x | s2cid = 29006987 | doi-access = free }}</ref> (n=0.56).