| Type: | Domain | Name: | Methionine repressor MetJ domain |
| Description: | Binding of a specific DNA fragment and S-adenosyl methionine (SAM) co-repressor molecules to the Escherichia colimethionine repressor (MetJ) leads to a significant reduction in dynamic flexibility of the ternary complex, with considerable entropy-enthalpy compensation, not necessarily involving any overall conformational change []. MetJ is a regulatory protein which when combined withS-adenosylmethionine (SAM) represses the expression of the methionine regulon and of enzymes involved in SAM synthesis. It is also autoregulated.The crystal structure of the met repressor-operator complex shows two dimeric repressor molecules bound to adjacent sites 8 base pairs apart on an 18-base-pairDNA fragment. Sequence specificity is achieved by insertion of double-stranded antiparallel protein beta-ribbons into the major groove of B-form DNA, with directhydrogen-bonding between amino-acid side chains and the base pairs. The repressor also recognises sequence-dependent distortion or flexibility of the operatorphosphate backbone, conferring specificity even for inaccessible base pairs []. | Short Name: | Met_repressor_MetJ_dom |
