1uvh
X-RAY STRUCTURE OF DPS FROM MYCOBACTERIUM SMEGMATIS
|
OverviewOverview
The structure and function of Mycobacterium smegmatis Dps (DNA-binding, proteins from starved cells) and of the protein studied by Gupta and, Chatterji, in which the C terminus that is used for binding DNA contains a, histidine tag, have been characterized in parallel. The native dodecamer, dissociated reversibly into dimers above pH 7.5 and below pH 6.0, with, apparent pK(a) values of approximately 7.65 and 4.75; at pH approximately, 4.0, dimers formed monomers. Based on structural analysis, the two, dissociation steps have been attributed to breakage of the salt bridges, between Glu(157) and Arg(99) located at the 3-fold symmetry axes and to, protonation of Asp(66) hydrogen-bonded to Lys(36) across the dimer, interface, respectively. The C-terminal tag did not affect subunit, dissociation, but altered DNA binding dramatically. At neutral pH, protonation of the histidine tag promoted DNA condensation, whereas in the, native C terminus, compensation of negative and positive charges led to, DNA binding without condensation. This different mode of interaction with, DNA has important functional consequences as indicated by the failure of, the native protein to protect DNA from DNase-mediated cleavage and by the, efficiency of the tagged protein in doing so as a result of DNA, sequestration in the condensates. Chemical protection of DNA from, oxidative damage is realized by Dps proteins in a multistep iron, oxidation/uptake/mineralization process. Dimers have a decreased, protection efficiency due to disruption of the dodecamer internal cavity, where iron is deposited and mineralized after oxidation at the ferroxidase, center.
About this StructureAbout this Structure
1UVH is a Single protein structure of sequence from Mycobacterium smegmatis with FE as ligand. Structure known Active Site: AC1. Full crystallographic information is available from OCA.
ReferenceReference
Reassessment of protein stability, DNA binding, and protection of Mycobacterium smegmatis Dps., Ceci P, Ilari A, Falvo E, Giangiacomo L, Chiancone E, J Biol Chem. 2005 Oct 14;280(41):34776-85. Epub 2005 Jul 19. PMID:16030020
Page seeded by OCA on Mon Nov 5 17:12:46 2007