Editing GroES (section)

== Structure and function ==

GroES exists as a ring-shaped [[oligomer]] of between six and eight identical subunits, while the 60 kDa chaperonin (cpn60, or groEL in bacteria) forms a [[secondary structure|structure]] comprising 2 stacked rings, each ring containing 7 identical [[protein subunit|subunits]].<ref name="pmid2897629">{{cite journal | vauthors = Hemmingsen SM, Woolford C, van der Vies SM, Tilly K, Dennis DT, Georgopoulos CP, Hendrix RW, Ellis RJ | title = Homologous plant and bacterial proteins chaperone oligomeric protein assembly | journal = Nature | volume = 333 | issue = 6171 | pages = 330–4  | date = May 1988 | pmid = 2897629 | doi = 10.1038/333330a0 | bibcode = 1988Natur.333..330H | s2cid = 4325057 }}</ref> These ring structures assemble by self-stimulation in the presence of Mg<sup>2+</sup>-ATP. The central cavity of the cylindrical cpn60 tetradecamer provides an isolated environment for [[protein folding]] whilst cpn-10 [[Molecular binding|bind]]s to cpn-60 and synchronizes the release of the [[protein folding|folded]] protein in an Mg<sup>2+</sup>-ATP dependent manner.<ref name="pmid1350777">{{cite journal | vauthors = Schmidt A, Schiesswohl M, Völker U, Hecker M, Schumann W | title = Cloning, sequencing, mapping, and transcriptional analysis of the groESL operon from Bacillus subtilis | journal = J. Bacteriol. | volume = 174 | issue = 12 | pages = 3993–9  | date = June 1992 | pmid = 1350777 | pmc = 206108 | doi =  10.1128/jb.174.12.3993-3999.1992}}</ref> The [[Molecular binding|binding]] of cpn10 to cpn60 [[Enzyme inhibitor|inhibits]] the weak ATPase activity of cpn60.

''[[Escherichia coli]]'' GroES has also been shown to bind [[Adenosine triphosphate|ATP]] cooperatively, and with an affinity comparable to that of GroEL.<ref name="pmid7901771">{{cite journal | vauthors = Martin J, Geromanos S, Tempst P, Hartl FU | title = Identification of nucleotide-binding regions in the chaperonin proteins GroEL and GroES | journal = Nature | volume = 366 | issue = 6452 | pages = 279–82  | date = November 1993 | pmid = 7901771 | doi = 10.1038/366279a0 | bibcode = 1993Natur.366..279M | s2cid = 4243962 }}</ref> Each GroEL subunit contains three [[structurally]] distinct domains: an apical, an intermediate and an equatorial domain. The apical domain contains the [[binding site]]s for both GroES and the unfolded protein substrate. The equatorial domain contains the ATP-binding site and most of the oligomeric contacts. The intermediate domain links the apical and equatorial [[protein domain|domains]] and transfers [[allosteric]] information between them. The GroEL oligomer is a tetradecamer, cylindrically shaped, that is organised in two heptameric rings stacked back to back. Each GroEL ring contains a central cavity, known as the `[[Anfinsen cage]]', that provides an isolated environment for protein folding. The identical 10 kDa subunits of GroES form a dome-like heptameric oligomer in solution. ATP binding to GroES may be important in charging the seven subunits of the interacting GroEL ring with ATP, to facilitate cooperative ATP binding and [[hydrolysis]] for substrate protein release.