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@ARTICLE{Fitter:42202,
      author       = {Fitter, J. and Haber-Pohlmeier, S.},
      title        = {{S}tructural {S}tability and {U}nfolding {P}roperties of
                      {T}hermostable bacterial alpha-amylases: {A} {C}omparative
                      {S}tudy on {H}omologous {E}nzymes},
      journal      = {Biochemistry},
      volume       = {43},
      issn         = {0006-2960},
      address      = {Columbus, Ohio},
      publisher    = {American Chemical Society},
      reportid     = {PreJuSER-42202},
      pages        = {9589 - 9599},
      year         = {2004},
      note         = {Record converted from VDB: 12.11.2012},
      abstract     = {In a comparative investigation on two thermostable
                      alpha-amylases [Bacillus amyloliquefaciens (BAA), T(m) = 86
                      degrees C and Bacillus licheniformis (BLA), T(m) = 101
                      degrees C], we studied thermal and guanidine hydrochloride
                      (GndHCl)-induced unfolding using fluorescence and CD
                      spectroscopy, as well as dynamic light scattering. Depletion
                      of calcium from specific ion-binding sites in the protein
                      structures reduces the melting temperature tremendously for
                      both alpha-amylases. The reduction is nearly the same for
                      both enzymes, namely, in the order of 50 degrees C. Thus,
                      the difference in thermostability between BLA and BAA
                      (DeltaT(m) approximately 15 degrees C) is related to
                      intrinsic properties of the respective protein structures
                      themselves and is not related to the strength of ion
                      binding. The thermal unfolding of both proteins is
                      characterized by a full disappearance of secondary structure
                      elements and by a concurrent expansion of the 3D structure.
                      GndHCl-induced unfolding also yields a fully vanishing
                      secondary structure but with more expanded 3D structures.
                      Both alpha-amylases remain much more compact upon thermal
                      unfolding as compared to the fully unfolded state induced by
                      chemical denaturants. Such rather compact thermal unfolded
                      structures lower the conformational entropy change during
                      the unfolding transition, which principally can contribute
                      to an increased thermal stability. Structural flexibilities
                      of both enzymes, as measured with tryptophan fluorescence
                      quenching, are almost identical for both enzymes in the
                      native states, as well as in the unfolded states.
                      Furthermore, we do not observe any difference in the
                      temperature dependence of the structural flexibilities
                      between BLA and BAA. These results indicate that
                      conformational dynamics on the time scale of our studies
                      seem not to be related to thermal stability or to thermal
                      adaptation.},
      keywords     = {Bacillus: enzymology / Bacterial Proteins: chemistry /
                      Enzyme Stability / Guanidine: chemistry / Kinetics / Light /
                      Protein Denaturation / Protein Folding / Scattering,
                      Radiation / Sequence Homology, Amino Acid / Spectrometry,
                      Fluorescence / Temperature / Thermodynamics /
                      alpha-Amylases: chemistry / Bacterial Proteins (NLM
                      Chemicals) / Guanidine (NLM Chemicals) / alpha-Amylases (NLM
                      Chemicals) / J (WoSType)},
      cin          = {IBI-2},
      ddc          = {570},
      cid          = {I:(DE-Juel1)VDB58},
      pnm          = {Neurowissenschaften},
      pid          = {G:(DE-Juel1)FUEK255},
      shelfmark    = {Biochemistry $\&$ Molecular Biology},
      typ          = {PUB:(DE-HGF)16},
      pubmed       = {pmid:15274613},
      UT           = {WOS:000222965100002},
      doi          = {10.1021/bi0493362},
      url          = {https://juser.fz-juelich.de/record/42202},
}