PDBsum entry 2hf5

Metal binding protein

PDB id: 2hf5

Contents

Protein chain

68 a.a. *

Metals

_CA ×2

* Residue conservation analysis

PDB id:

2hf5

Name:

Metal binding protein

Title:

The structure and function of a novel two-site calcium-binding fragment of calmodulin

Structure:

Calmodulin. Chain: a. Fragment: ef-hands 2 and 3 (residues 46-113). Synonym: cam. Engineered: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Gene: calm1, calm, cam, cam1, calm2, cam2, camb, calm3, cam3, camc, camiii. Expressed in: escherichia coli. Expression_system_taxid: 562.

NMR struc:

20 models

Authors:

T.M.Lakowski,G.M.Lee,R.E.Reid,L.P.Mcintosh

Key ref:

T.M.Lakowski et al. (2007). Calcium-induced folding of a fragment of calmodulin composed of EF-hands 2 and 3. Protein Sci, 16, 1119-1132. PubMed id: 17473011 DOI: 10.1110/ps.072777107

Date:

23-Jun-06 Release date: 01-May-07

Protein chain

P0DP23  (CALM1_HUMAN) -  Calmodulin-1 from Homo sapiens

Seq: 149 a.a.

Struc: 68 a.a.

DOI no: 10.1110/ps.072777107

Protein Sci 16:1119-1132 (2007)

PubMed id: 17473011

Calcium-induced folding of a fragment of calmodulin composed of EF-hands 2 and 3.

T.M.Lakowski, G.M.Lee, M.Okon, R.E.Reid, L.P.McIntosh.

ABSTRACT

Calmodulin (CaM) is an EF-hand protein composed of two calcium (Ca(2+))-binding EF-hand motifs in its N-domain (EF-1 and EF-2) and two in its C-domain (EF-3 and EF-4). In this study, we examined the structure, dynamics, and Ca(2+)-binding properties of a fragment of CaM containing only EF-2 and EF-3 and the intervening linker sequence (CaM2/3). Based on NMR spectroscopic analyses, Ca(2+)-free CaM2/3 is predominantly unfolded, but upon binding Ca(2+), adopts a monomeric structure composed of two EF-hand motifs bridged by a short antiparallel beta-sheet. Despite having an "even-odd" pairing of EF-hands, the tertiary structure of CaM2/3 is similar to both the "odd-even" paired N- and C-domains of Ca(2+)-ligated CaM, with the conformationally flexible linker sequence adopting the role of an inter-EF-hand loop. However, unlike either CaM domain, CaM2/3 exhibits stepwise Ca(2+) binding with a K (d1) = 30 +/- 5 microM to EF-3, and a K (d2) > 1000 microM to EF-2. Binding of the first equivalent of Ca(2+) induces the cooperative folding of CaM2/3. In the case of native CaM, stacking interactions between four conserved aromatic residues help to hold the first and fourth helices of each EF-hand domain together, while the loop between EF-hands covalently tethers the second and third helices. In contrast, these aromatic residues lie along the second and third helices of CaM2/3, and thus are positioned adjacent to the loop between its "even-odd" paired EF-hands. This nonnative hydrophobic core packing may contribute to the weak Ca(2+) affinity exhibited by EF-2 in the context of CaM2/3.

Selected figure(s)

Figure 5.
Figure 5. CaM2/3 superimposed onto the domains of CaM. (A,B) The

Figure 6.
Figure 6. Backbone 15 N relaxation data for Ca 2+ -saturated CaM2/3. (A) The longitudinal (T1) and (B) transverse (T2) 15 N relaxation

The above figures are reprinted by permission from the Protein Society: Protein Sci (2007, 16, 1119-1132) copyright 2007.

Figures were selected by an automated process.