Transient protein complexes form and break down transiently ''in vivo'', whereas permanent complexes have a relatively long half-life. Typically, the obligate interactions (protein-protein interactions in an obligate complex) are permanent, whereas non-obligate interactions have been found to be either permanent or transient.<ref name = "Amoutzias_2010"/> Note that there is no clear distinction between obligate and non-obligate interaction, rather there exist a continuum between them which depends on various conditions e.g. pH, protein concentration etc.<ref name="pmid12853464">{{cite journal | author = Nooren IM, Thornton JM | title = Diversity of protein-protein interactions | journal = EMBO J. | volume = 22 | issue = 14 | pages = 3486–92 |date=July 2003 | pmid = 12853464 | pmc = 165629 | doi = 10.1093/emboj/cdg359 }}</ref> However, there are important distinctions between the properties of transient and permanent/stable interactions: stable interactions are highly conserved but transient interactions are far less conserved, interacting proteins on the two sides of a stable interaction have more tendency of being co-expressed than those of a transient interaction (in fact, co-expression probability between two transiently interacting proteins is not higher than two random proteins), and transient interactions are much less co-localized than stable interactions.<ref name="pmid17535438">{{cite journal | author = Brown KR, Jurisica I | title = Unequal evolutionary conservation of human protein interactions in interologous networks | journal = Genome Biol. | volume = 8 | issue = 5 | pages = R95 | year = 2007 | pmid = 17535438 | pmc = 1929159 | doi = 10.1186/gb-2007-8-5-r95 }}</ref> Though, transient by nature, transient interactions are very important for cell biology: human interactome is enriched in such interactions, these interactions are the dominating players of gene regulation and signal transduction, and proteins with ''intrinsically disordered regions'' (IDR: regions in protein that show dynamic inter-converting structures in the native state) are found to be enriched in transient regulatory and signaling interactions.<ref name = "Amoutzias_2010"/>
=== FuzzyComplexo complexborroso ===
FuzzyOs proteincomplexos complexesproteicos haveborrosos more(''fuzzy thancomplexes'') oneteñen structuralmáis formdunha orformaestrutural dynamicou structuralun disorderdesorde inestrutural dinámico theno boundestado stateunido.<ref name="pmid18054235">{{cite journal | author = Tompa P, Fuxreiter M | title = Fuzzy complexes: polymorphism and structural disorder in protein-protein interactions | journal = Trends Biochem. Sci. | volume = 33 | issue = 1 | pages = 2–8 |date=January 2008 | pmid = 18054235 | doi = 10.1016/j.tibs.2007.10.003 }}</ref> ThisIstosignifica meansque thatas proteinsproteínas maypoden notnon fold[[pregamento completelydas inproteínas|pregarse]] eithercompletamente transienten orcomplexos permanenttransitorios complexesou permenentes. ConsequentlyEn consecuencia, specificcomplexos complexesespecíficos canpoden haveter ambiguousinteraccións interactionsambiguas, whichque varyvarían accordingde toacordo thecos environmentalsinais signalsambientais. HencePor differenttanto, ensembleas ofdiferentes structuresensamblaxes resultdas inestruturas differentdan lugar a distintas (evenmesmo ás veces oppositeopostas) biologicalfuncións functionsbiolóxicas.<ref name="pmid21927770">{{cite journal | author = Fuxreiter M | title = Fuzziness: linking regulation to protein dynamics | journal = Mol Biosyst | volume = 8 | issue = 1 | pages = 168–77 |date=January 2012 | pmid = 21927770 | doi = 10.1039/c1mb05234a }}</ref> Post-translationalAs modifications[[modificación postrducional|modificacións postraducionais]], proteinas interactions[[interacción orproteína-proteína|interaccións alternativeentre splicingproteínas]] modulateou theo [[conformationalempalme ensemblesalternativo]] ofmodulan fuzzyas complexes[[ensamblaxe conformacional|ensamblaxes conformacionais]] destes complexos borrosos, topara fine-tuneaxustar affinityfinamente ora specificityafinidade ofou interactionsespecificidade das interaccións. Estes Thesemecanismos mechanismsson arecon oftenfrecuencia usedutilizados forpara regulationa regulación como parte withinda themaquinaria eukaryoticde transcriptiontranscrición machineryeucariótica.<ref name="pmid21620710">{{cite journal | author = Fuxreiter M, Simon I, Bondos S | title = Dynamic protein-DNA recognition: beyond what can be seen | journal = Trends Biochem. Sci. | volume = 36 | issue = 8 | pages = 415–23 |date=August 2011 | pmid = 21620710 | doi = 10.1016/j.tibs.2011.04.006 }}</ref>
