2pq3: Difference between revisions
New page: left|200px<br /><applet load="2pq3" size="350" color="white" frame="true" align="right" spinBox="true" caption="2pq3, resolution 1.30Å" /> '''N-Terminal Calmoduli... |
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==Overview== | ==Overview== | ||
Calmodulin (CaM) is a 16.8-kDa calcium-binding protein involved in | Calmodulin (CaM) is a 16.8-kDa calcium-binding protein involved in calcium-signal transduction. It is the canonical member of the EF-hand family of proteins, which are characterized by a helix-loop-helix calcium-binding motif. CaM is composed of N- and C-terminal globular domains (N-CaM and C-CaM), and within each domain there are two EF-hand motifs. Upon binding calcium, CaM undergoes a significant, global conformational change involving reorientation of the four helix bundles in each of its two domains. This conformational change upon ion binding is a key component of the signal transduction and regulatory roles of CaM, yet the precise nature of this transition is still unclear. Here, we present a 1.3-A structure of zinc-bound N-terminal calmodulin (N-CaM) solved by single-wavelength anomalous diffraction phasing of a selenomethionyl N-CaM. Our zinc-bound N-CaM structure differs from previously reported CaM structures and resembles calcium-free apo-calmodulin (apo-CaM), despite the zinc binding to both EF-hand motifs. Structural comparison with calcium-free apo-CaM, calcium-loaded CaM, and a cross-linked calcium-loaded CaM suggests that our zinc-bound N-CaM reveals an intermediate step in the initiation of metal ion binding at the first EF-hand motif. Our data also suggest that metal ion coordination by two key residues in the first metal-binding site represents an initial step in the conformational transition induced by metal binding. This is followed by reordering of the N-terminal region of the helix exiting from this first binding loop. This conformational switch should be incorporated into models of either stepwise conformational transition or flexible, dynamic energetic state sampling-based transition. | ||
==About this Structure== | ==About this Structure== | ||
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[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Guo, Q.]] | [[Category: Guo, Q.]] | ||
[[Category: Tang, W | [[Category: Tang, W J.]] | ||
[[Category: Warren, J | [[Category: Warren, J T.]] | ||
[[Category: CAC]] | [[Category: CAC]] | ||
[[Category: ZN]] | [[Category: ZN]] | ||
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[[Category: n-terminal calmodulin]] | [[Category: n-terminal calmodulin]] | ||
''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 18:31:56 2008'' | ||
Revision as of 19:31, 21 February 2008
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N-Terminal Calmodulin Zn-Trapped Intermediate
OverviewOverview
Calmodulin (CaM) is a 16.8-kDa calcium-binding protein involved in calcium-signal transduction. It is the canonical member of the EF-hand family of proteins, which are characterized by a helix-loop-helix calcium-binding motif. CaM is composed of N- and C-terminal globular domains (N-CaM and C-CaM), and within each domain there are two EF-hand motifs. Upon binding calcium, CaM undergoes a significant, global conformational change involving reorientation of the four helix bundles in each of its two domains. This conformational change upon ion binding is a key component of the signal transduction and regulatory roles of CaM, yet the precise nature of this transition is still unclear. Here, we present a 1.3-A structure of zinc-bound N-terminal calmodulin (N-CaM) solved by single-wavelength anomalous diffraction phasing of a selenomethionyl N-CaM. Our zinc-bound N-CaM structure differs from previously reported CaM structures and resembles calcium-free apo-calmodulin (apo-CaM), despite the zinc binding to both EF-hand motifs. Structural comparison with calcium-free apo-CaM, calcium-loaded CaM, and a cross-linked calcium-loaded CaM suggests that our zinc-bound N-CaM reveals an intermediate step in the initiation of metal ion binding at the first EF-hand motif. Our data also suggest that metal ion coordination by two key residues in the first metal-binding site represents an initial step in the conformational transition induced by metal binding. This is followed by reordering of the N-terminal region of the helix exiting from this first binding loop. This conformational switch should be incorporated into models of either stepwise conformational transition or flexible, dynamic energetic state sampling-based transition.
About this StructureAbout this Structure
2PQ3 is a Single protein structure of sequence from Rattus norvegicus with and as ligands. Full crystallographic information is available from OCA.
ReferenceReference
A 1.3-A structure of zinc-bound N-terminal domain of calmodulin elucidates potential early ion-binding step., Warren JT, Guo Q, Tang WJ, J Mol Biol. 2007 Nov 23;374(2):517-27. Epub 2007 Sep 21. PMID:17942116
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