1g8e
From Proteopedia
(New page: 200px<br /><applet load="1g8e" size="450" color="white" frame="true" align="right" spinBox="true" caption="1g8e, resolution 1.8Å" /> '''CRYSTAL STRUCTURE OF ...) |
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| - | [[Image:1g8e.gif|left|200px]]<br /><applet load="1g8e" size=" | + | [[Image:1g8e.gif|left|200px]]<br /><applet load="1g8e" size="350" color="white" frame="true" align="right" spinBox="true" |
caption="1g8e, resolution 1.8Å" /> | caption="1g8e, resolution 1.8Å" /> | ||
'''CRYSTAL STRUCTURE OF FLHD FROM ESCHERICHIA COLI'''<br /> | '''CRYSTAL STRUCTURE OF FLHD FROM ESCHERICHIA COLI'''<br /> | ||
==Overview== | ==Overview== | ||
| - | FlhD is a 13.3 kDa transcriptional activator protein of flagellar genes | + | FlhD is a 13.3 kDa transcriptional activator protein of flagellar genes and a global regulator. FlhD activates the transcription of class II operons in the flagellar regulon when complexed with a second protein FlhC (21.5 kDa). FlhD also regulates other expression systems in Escherichia coli. We are seeking to understand this plasticity of FlhD's DNA-binding specificity and, to this end, we have determined the crystal structure of the isolated FlhD protein. The structure was solved by substituting seleno-methionine for natural sulphur-methionine in FlhD, crystallizing the protein and determining the structure factor phases by the method of multiple-energy anomalous dispersion (MAD). The FlhD protein is dimeric. The dimer is tightly coupled, with an intimate contact surface, implying that the dimer does not easily dissociate. The FlhD monomer is predominantly alpha-helical. The C-termini of both FlhD monomers (residues 83-116) are completely disrupted by crystal packing, implying that this region of FlhD is highly flexible. However, part of the C-terminus structure in chain A (residues 83-98) was modelled using a native FlhD crystal. What is seen in chain A suggests a classic DNA-binding, helix-turn-helix (HTH) motif. FlhD does not bind DNA by itself, so it may be that the DNA-binding HTH motif becomes rigidly defined only when FlhD forms a complex with some other protein, such as FlhC. If this were true, it might explain how FlhD exhibits plasticity in its DNA-binding specificity, as each partner protein with which it forms a complex could allosterically affect the binding specificity of its HTH motif. A disulphide bridge is seen between the unique cysteine residues (Cys-65) of FlhD native homodimers. Alanine substitution at Cys-65 does not affect FlhD transcription activator activity, suggesting that the disulphide bond is not necessary for either dimer stability or this function of FlhD. Electrostatic potential analysis indicates that dimeric FlhD has a negatively charged surface. |
==About this Structure== | ==About this Structure== | ||
| - | 1G8E is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http:// | + | 1G8E is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Escherichia_coli Escherichia coli]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1G8E OCA]. |
==Reference== | ==Reference== | ||
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[[Category: Escherichia coli]] | [[Category: Escherichia coli]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
| - | [[Category: Alkire, R | + | [[Category: Alkire, R W.]] |
[[Category: Campos, A.]] | [[Category: Campos, A.]] | ||
[[Category: Matsumura, P.]] | [[Category: Matsumura, P.]] | ||
| - | [[Category: Westbrook, E | + | [[Category: Westbrook, E M.]] |
| - | [[Category: Zhang, R | + | [[Category: Zhang, R G.]] |
[[Category: dna binding protein]] | [[Category: dna binding protein]] | ||
[[Category: genetic regulator]] | [[Category: genetic regulator]] | ||
| - | ''Page seeded by [http:// | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:47:13 2008'' |
Revision as of 10:47, 21 February 2008
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CRYSTAL STRUCTURE OF FLHD FROM ESCHERICHIA COLI
Overview
FlhD is a 13.3 kDa transcriptional activator protein of flagellar genes and a global regulator. FlhD activates the transcription of class II operons in the flagellar regulon when complexed with a second protein FlhC (21.5 kDa). FlhD also regulates other expression systems in Escherichia coli. We are seeking to understand this plasticity of FlhD's DNA-binding specificity and, to this end, we have determined the crystal structure of the isolated FlhD protein. The structure was solved by substituting seleno-methionine for natural sulphur-methionine in FlhD, crystallizing the protein and determining the structure factor phases by the method of multiple-energy anomalous dispersion (MAD). The FlhD protein is dimeric. The dimer is tightly coupled, with an intimate contact surface, implying that the dimer does not easily dissociate. The FlhD monomer is predominantly alpha-helical. The C-termini of both FlhD monomers (residues 83-116) are completely disrupted by crystal packing, implying that this region of FlhD is highly flexible. However, part of the C-terminus structure in chain A (residues 83-98) was modelled using a native FlhD crystal. What is seen in chain A suggests a classic DNA-binding, helix-turn-helix (HTH) motif. FlhD does not bind DNA by itself, so it may be that the DNA-binding HTH motif becomes rigidly defined only when FlhD forms a complex with some other protein, such as FlhC. If this were true, it might explain how FlhD exhibits plasticity in its DNA-binding specificity, as each partner protein with which it forms a complex could allosterically affect the binding specificity of its HTH motif. A disulphide bridge is seen between the unique cysteine residues (Cys-65) of FlhD native homodimers. Alanine substitution at Cys-65 does not affect FlhD transcription activator activity, suggesting that the disulphide bond is not necessary for either dimer stability or this function of FlhD. Electrostatic potential analysis indicates that dimeric FlhD has a negatively charged surface.
About this Structure
1G8E is a Single protein structure of sequence from Escherichia coli. Full crystallographic information is available from OCA.
Reference
Crystal structure of the global regulator FlhD from Escherichia coli at 1.8 A resolution., Campos A, Zhang RG, Alkire RW, Matsumura P, Westbrook EM, Mol Microbiol. 2001 Feb;39(3):567-80. PMID:11169099
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