2pq3 | pdb_00002pq3
N-Terminal Calmodulin Zn-Trapped Intermediate
Structural highlights
Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedCalmodulin (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. 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[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
| ||||||||||||||||||||
