Family

Methionine repressor MetJ (IPR002084)

Short name: Met_repressor_MetJ

Family relationships

None.

Description

Binding of a specific DNA fragment and S-adenosyl methionine (SAM) co-repressor molecules to the Escherichia coli methionine 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 [PMID: 8026581]. MetJ is a regulatory protein which when combined with S-adenosylmethionine (SAM) represses the expression of the methionine regulon and of enzymes involved in SAM synthesis. It is also autoregulated.

MetJ binds arrays of two to five adjacent copies of an eight base-pair 'metbox' sequence. MetJ forms sufficiently strong interactions with the sugar-phosphate backbone to accomodate sequence variation in natural operators. However, it is very sensitive to particular base changes in the operator. MetJ exists as a homodimer [PMID: 1943695, PMID: 10986458, PMID: 8092669].

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-pair DNA fragment. Sequence specificity is achieved by insertion of double-stranded antiparallel protein beta-ribbons into the major groove of B-form DNA, with direct hydrogen-bonding between amino-acid side chains and the base pairs. The repressor also recognises sequence-dependent distortion or flexibility of the operator phosphate backbone, conferring specificity even for inaccessible base pairs [PMID: 1406951].

GO terms

Biological Process

GO:0006555 methionine metabolic process
GO:0006355 regulation of transcription, DNA-templated

Molecular Function

GO:0003700 transcription factor activity, sequence-specific DNA binding

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
HAMAP
CDD
ProDom
Pfam