1d1m: Difference between revisions
New page: left|200px<br /><applet load="1d1m" size="450" color="white" frame="true" align="right" spinBox="true" caption="1d1m, resolution 2.05Å" /> '''CRYSTAL STRUCTURE OF... |
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[[Image:1d1m.gif|left|200px]]<br /><applet load="1d1m" size=" | [[Image:1d1m.gif|left|200px]]<br /><applet load="1d1m" size="350" color="white" frame="true" align="right" spinBox="true" | ||
caption="1d1m, resolution 2.05Å" /> | caption="1d1m, resolution 2.05Å" /> | ||
'''CRYSTAL STRUCTURE OF CRO K56-[DGEVK]-F58W MUTANT'''<br /> | '''CRYSTAL STRUCTURE OF CRO K56-[DGEVK]-F58W MUTANT'''<br /> | ||
==Overview== | ==Overview== | ||
It was previously shown that the Cro repressor from phage lambda, which is | It was previously shown that the Cro repressor from phage lambda, which is a dimer, can be converted into a stable monomer by a five-amino acid insertion. Phe58 is the key residue involved in this transition, switching from interactions which stabilize the dimer to those which stabilize the monomer. Structural studies, however, suggested that Phe58 did not penetrate into the core of the monomer as well as it did into the native dimer. This was strongly supported by the finding that certain core-repacking mutations, including in particular, Phe58-->Trp, increased the stability of the monomer. Unexpectedly, the same substitution also increased the stability of the native dimer. At the same time it decreased the affinity of the dimer for operator DNA. Here we describe the crystal structures of the Cro F58W mutant, both as the monomer and as the dimer. The F58W monomer crystallized in a form different from that of the original monomer. In contrast to that structure, which resembled the DNA-bound form of Cro, the F58W monomer is closer in structure to wild-type (i.e. non-bound) Cro. The F58W dimer also crystallizes in a form different from the native dimer but has a remarkably similar overall structure which tends to confirm the large changes in conformation of Cro on binding DNA. Introduction of Trp58 perturbs the position occupied by the side-chain of Arg38, a DNA-contact residue, providing a structural explanation for the reduction in DNA-binding affinity.The improved thermal stability is seen to be due to the enhanced solvent transfer free energy of Trp58 relative to Phe58, supplemented in the dimer structure, although not the monomer, by a reduction in volume of internal cavities. | ||
==About this Structure== | ==About this Structure== | ||
1D1M is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Enterobacteria_phage_lambda Enterobacteria phage lambda]. Full crystallographic information is available from [http:// | 1D1M is a [http://en.wikipedia.org/wiki/Single_protein Single protein] structure of sequence from [http://en.wikipedia.org/wiki/Enterobacteria_phage_lambda Enterobacteria phage lambda]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=1D1M OCA]. | ||
==Reference== | ==Reference== | ||
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[[Category: Enterobacteria phage lambda]] | [[Category: Enterobacteria phage lambda]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Matthews, B | [[Category: Matthews, B W.]] | ||
[[Category: Mollah, A | [[Category: Mollah, A K.]] | ||
[[Category: Mossing, M | [[Category: Mossing, M C.]] | ||
[[Category: Rupert, P | [[Category: Rupert, P B.]] | ||
[[Category: helix-turn-helix]] | [[Category: helix-turn-helix]] | ||
''Page seeded by [http:// | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 12:11:58 2008'' | ||
Revision as of 13:11, 21 February 2008
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CRYSTAL STRUCTURE OF CRO K56-[DGEVK]-F58W MUTANT
OverviewOverview
It was previously shown that the Cro repressor from phage lambda, which is a dimer, can be converted into a stable monomer by a five-amino acid insertion. Phe58 is the key residue involved in this transition, switching from interactions which stabilize the dimer to those which stabilize the monomer. Structural studies, however, suggested that Phe58 did not penetrate into the core of the monomer as well as it did into the native dimer. This was strongly supported by the finding that certain core-repacking mutations, including in particular, Phe58-->Trp, increased the stability of the monomer. Unexpectedly, the same substitution also increased the stability of the native dimer. At the same time it decreased the affinity of the dimer for operator DNA. Here we describe the crystal structures of the Cro F58W mutant, both as the monomer and as the dimer. The F58W monomer crystallized in a form different from that of the original monomer. In contrast to that structure, which resembled the DNA-bound form of Cro, the F58W monomer is closer in structure to wild-type (i.e. non-bound) Cro. The F58W dimer also crystallizes in a form different from the native dimer but has a remarkably similar overall structure which tends to confirm the large changes in conformation of Cro on binding DNA. Introduction of Trp58 perturbs the position occupied by the side-chain of Arg38, a DNA-contact residue, providing a structural explanation for the reduction in DNA-binding affinity.The improved thermal stability is seen to be due to the enhanced solvent transfer free energy of Trp58 relative to Phe58, supplemented in the dimer structure, although not the monomer, by a reduction in volume of internal cavities.
About this StructureAbout this Structure
1D1M is a Single protein structure of sequence from Enterobacteria phage lambda. Full crystallographic information is available from OCA.
ReferenceReference
The structural basis for enhanced stability and reduced DNA binding seen in engineered second-generation Cro monomers and dimers., Rupert PB, Mollah AK, Mossing MC, Matthews BW, J Mol Biol. 2000 Mar 3;296(4):1079-90. PMID:10686105
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