1bli: Difference between revisions

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==Overview==

BACKGROUND: The structural basis as to how metals regulate the functional, state of a protein by altering or stabilizing its conformation has been, characterized in relatively few cases because the metal-free form of the, protein is often partially disordered and unsuitable for crystallographic, analysis. This is not the case, however, for Bacillus licheniformis, alpha-amylase (BLA) for which the structure of the metal-free form is, available. BLA is a hyperthermostable enzyme which is widely used in, biotechnology, for example in the breakdown of starch or as a component of, detergents. The determination of the structure of BLA in the, metal-containing form, together with comparisons to the apo enzyme, will, help us to understand the way in which metal ions can regulate enzyme, activity. RESULTS: We report here the crystal structure of native, metal-containing BLA. The structure shows that the calcium-binding site, which is conserved in all alpha-amylases forms part of an unprecedented, linear triadic metal array, with two calcium ions flanking a central, sodium ion. A region around the metal triad comprising 21 residues, exhibits a conformational change involving a helix unwinding and a, disorder-->order transition compared to the structure of metal-free BLA., Another calcium ion, not previously observed in alpha-amylases, is located, at the interface between domains A and C. CONCLUSIONS: We present a, structural description of a major conformational rearrangement mediated by, metal ions. The metal induced disorder-->order transition observed in BLA, leads to the formation of the extended substrate-binding site and explains, on a structural level the calcium dependency of alpha-amylases. Sequence, comparisons indicate that the unique Ca-Na-Ca metal triad and the, additional calcium ion located between domains A and C might be found, exclusively in bacterial alpha-amylases which show increased, thermostability. The information presented here may help in the rational, design of mutants with enhanced performance in biotechnological, applications.

BACKGROUND: The structural basis as to how metals regulate the functional state of a protein by altering or stabilizing its conformation has been characterized in relatively few cases because the metal-free form of the protein is often partially disordered and unsuitable for crystallographic analysis. This is not the case, however, for Bacillus licheniformis alpha-amylase (BLA) for which the structure of the metal-free form is available. BLA is a hyperthermostable enzyme which is widely used in biotechnology, for example in the breakdown of starch or as a component of detergents. The determination of the structure of BLA in the metal-containing form, together with comparisons to the apo enzyme, will help us to understand the way in which metal ions can regulate enzyme activity. RESULTS: We report here the crystal structure of native, metal-containing BLA. The structure shows that the calcium-binding site which is conserved in all alpha-amylases forms part of an unprecedented linear triadic metal array, with two calcium ions flanking a central sodium ion. A region around the metal triad comprising 21 residues exhibits a conformational change involving a helix unwinding and a disorder-->order transition compared to the structure of metal-free BLA. Another calcium ion, not previously observed in alpha-amylases, is located at the interface between domains A and C. CONCLUSIONS: We present a structural description of a major conformational rearrangement mediated by metal ions. The metal induced disorder-->order transition observed in BLA leads to the formation of the extended substrate-binding site and explains on a structural level the calcium dependency of alpha-amylases. Sequence comparisons indicate that the unique Ca-Na-Ca metal triad and the additional calcium ion located between domains A and C might be found exclusively in bacterial alpha-amylases which show increased thermostability. The information presented here may help in the rational design of mutants with enhanced performance in biotechnological applications.

==About this Structure==

Line 30:

[[Category: thermostability]]

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@@ Line 4: / Line 4: @@
 ==Overview==
-BACKGROUND: The structural basis as to how metals regulate the functional, state of a protein by altering or stabilizing its conformation has been, characterized in relatively few cases because the metal-free form of the, protein is often partially disordered and unsuitable for crystallographic, analysis. This is not the case, however, for Bacillus licheniformis, alpha-amylase (BLA) for which the structure of the metal-free form is, available. BLA is a hyperthermostable enzyme which is widely used in, biotechnology, for example in the breakdown of starch or as a component of, detergents. The determination of the structure of BLA in the, metal-containing form, together with comparisons to the apo enzyme, will, help us to understand the way in which metal ions can regulate enzyme, activity. RESULTS: We report here the crystal structure of native, metal-containing BLA. The structure shows that the calcium-binding site, which is conserved in all alpha-amylases forms part of an unprecedented, linear triadic metal array, with two calcium ions flanking a central, sodium ion. A region around the metal triad comprising 21 residues, exhibits a conformational change involving a helix unwinding and a, disorder--&gt;order transition compared to the structure of metal-free BLA., Another calcium ion, not previously observed in alpha-amylases, is located, at the interface between domains A and C. CONCLUSIONS: We present a, structural description of a major conformational rearrangement mediated by, metal ions. The metal induced disorder--&gt;order transition observed in BLA, leads to the formation of the extended substrate-binding site and explains, on a structural level the calcium dependency of alpha-amylases. Sequence, comparisons indicate that the unique Ca-Na-Ca metal triad and the, additional calcium ion located between domains A and C might be found, exclusively in bacterial alpha-amylases which show increased, thermostability. The information presented here may help in the rational, design of mutants with enhanced performance in biotechnological, applications.
+BACKGROUND: The structural basis as to how metals regulate the functional state of a protein by altering or stabilizing its conformation has been characterized in relatively few cases because the metal-free form of the protein is often partially disordered and unsuitable for crystallographic analysis. This is not the case, however, for Bacillus licheniformis alpha-amylase (BLA) for which the structure of the metal-free form is available. BLA is a hyperthermostable enzyme which is widely used in biotechnology, for example in the breakdown of starch or as a component of detergents. The determination of the structure of BLA in the metal-containing form, together with comparisons to the apo enzyme, will help us to understand the way in which metal ions can regulate enzyme activity. RESULTS: We report here the crystal structure of native, metal-containing BLA. The structure shows that the calcium-binding site which is conserved in all alpha-amylases forms part of an unprecedented linear triadic metal array, with two calcium ions flanking a central sodium ion. A region around the metal triad comprising 21 residues exhibits a conformational change involving a helix unwinding and a disorder--&gt;order transition compared to the structure of metal-free BLA. Another calcium ion, not previously observed in alpha-amylases, is located at the interface between domains A and C. CONCLUSIONS: We present a structural description of a major conformational rearrangement mediated by metal ions. The metal induced disorder--&gt;order transition observed in BLA leads to the formation of the extended substrate-binding site and explains on a structural level the calcium dependency of alpha-amylases. Sequence comparisons indicate that the unique Ca-Na-Ca metal triad and the additional calcium ion located between domains A and C might be found exclusively in bacterial alpha-amylases which show increased thermostability. The information presented here may help in the rational design of mutants with enhanced performance in biotechnological applications.
 ==About this Structure==
@@ Line 30: / Line 30: @@
 [[Category: thermostability]]
-''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Sun Feb  3 09:33:18 2008''
+''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 11:56:37 2008''