1mjm

METHIONINE APOREPRESSOR MUTANT (Q44K) COMPLEXED TO HALF OF THE CONSENSUS OPERATOR SEQUENCE

spinqualitylabelsall models 1mjm, resolution 2.20Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1mjm is a 4 chain structure with sequence from Escherichia coli. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.2Å Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function METJ_ECOLI This regulatory protein, when combined with SAM (S-adenosylmethionine) represses the expression of the methionine regulon and of enzymes involved in SAM synthesis. It is also autoregulated.[HAMAP-Rule:MF_00744] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed BACKGROUND: The methionine repressor, MetJ, represses the transcription of genes involved in methionine biosynthesis by binding to arrays of two to five adjacent copies of an eight base-pair 'metbox' sequence. Naturally occurring operators differ from the consensus sequence to a greater extent as the number of metboxes increases. MetJ, while accommodating this sequence variation in natural operators, is very sensitive to particular base changes, even where bases are not directly contacted in the crystal structure of a complex formed between the repressor and consensus operator. RESULTS: Here we report the high-resolution structure of a MetJ mutant, Q44K, bound to the consensus operator sequence (Q44Kwt19) and two related sequences containing mutations at sites believed to be important for indirect readout at non-contacted bases. The overall structure of the Q44Kwt19 complex is very similar to the wild-type complex, but there are small variations in sugar-phosphate backbone conformation and direct contacts to the DNA bases. The mutant complexes show a mixture of direct and indirect readout of sequence variations, with differences in direct contacts and DNA conformation. CONCLUSIONS: Comparison of the wild-type and mutant repressor-operator complexes shows that the repressor makes sufficiently strong interactions with the sugar-phosphate backbone to accommodate some variation in operator sequence with minor changes in direct bases contacts. The reduction in repressor affinity for the two mutant repressor complexes can be partially attributed to a loss in direct contacts to the DNA. In one case, however, the replacement of a flexible TA base-step leads to an unfavourable DNA conformation that reduces the stability of the repressor-operator complex. Direct and indirect readout in mutant Met repressor-operator complexes.,Garvie CW, Phillips SE Structure. 2000 Sep 15;8(9):905-14. PMID:10986458 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See Also Met repressor

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