PDBsum entry 2ev7

Metal binding protein

PDB id: 2ev7

Contents

Protein chain

64 a.a.

Metals

_LA

Obsolete entry

PDB id:

2ev7

Name:

Metal binding protein

Title:

The refined structure of c-terminal domain of an ef-hand calcium binding protein from entamoeba histolytica

Structure:

Calcium-binding protein. Chain: a. Fragment: c-terminal domain. Synonym: cabp

Source:

Entamoeba histolytica

NMR struc:

16 models

Authors:

S.M.Mustafi,K.V.R.Chary,S.Mukherji

Key ref:

S.M.Mustafi et al. (2006). Structural basis for the observed differential magnetic anisotropic tensorial values in calcium binding proteins. Proteins, 65, 656-669. PubMed id: 16981203 DOI: 10.1002/prot.21121

Date:

31-Oct-05 Release date: 27-Jun-06

Protein chain

P38505  (CABP1_ENTH1) -  Calcium-binding protein 1 from Entamoeba histolytica (strain ATCC 30459 / HM-1:IMSS / ABRM)

Seq: 134 a.a.

Struc: 64 a.a.

DOI no: 10.1002/prot.21121

Proteins 65:656-669 (2006)

PubMed id: 16981203

Structural basis for the observed differential magnetic anisotropic tensorial values in calcium binding proteins.

S.M.Mustafi, S.Mukherjee, K.V.Chary, G.Cavallaro.

ABSTRACT

Lanthanide ions (Ln(3+)), which have ionic radii similar to those of Ca(2+), can displace the latter in a calcium binding protein, without affecting its tertiary structure. The paramagnetic Ln(3+) possesses large anisotropic magnetic susceptibilities and produce pseudocontact shifts (PCSs), which have r(-3) dependence. The PCS can be seen for spins as far as 45 A from the paramagnetic ion. They aid in structure refinement of proteins by providing long-range distance constraints. Besides, they can be used to determine the interdomain orientation in multidomain proteins. This is particularly important in the context of a calcium binding protein from Entamoeba histolytica (EhCaBP), which consists of two globular domains connected by a flexible linker region containing 8 residues. As a first step to obtain the interdomain orientation in EhCaBP, a suite of 2D and 3D heteronuclear experiments were recorded on EhCaBP by displacing calcium with Ce(3+), Ho(3+), Er(3+), Tm(3+), Dy(3+), and Yb(3+) ions in separate experiments, and the PCS of (1)H(N) and (15)N spins were measured. Such data have been used in the refinement of the individual domain structures of the protein in parallel with the calculation of the respective magnetic anisotropy tensorial values, which differ substantially (2.1-2.8 times) from what is found in other Ca(2+) binding loops. This study provides a structural basis for such variations in the magnetic anisotropy tensorial values.

Selected figure(s)

Figure 2.
Figure 2. The dipolar nature of pseudo-contact interaction, under point-point dipole approximation. The Ln^3+ ion is taken as the origin of the co-ordinate system; r is the distance of a particular nucleus in the protein from its paramagnetic center.

Figure 7.
Figure 7. Various ^15N and ^1H^N PCS shifts seen in the C-terminal domain of (Dy^3+/Tm^3+)(Ca^2+)[3]-EhCaBP, in (Dy^3+)(Ca^2+)-Parvalbumin and in the N-terminal domain of (Tm ^3+)(Ca^2+)[3]Calmodulin (N60D), depicted as spheres using MOLMOL. The red spheres represent the negative shifts, while green ones are positive shifts. The radii of the spheres are proportional to the magnitude of the observed shifts. The shifts observed in (Dy^3+)(Ca^2+)-Parvalbumin and in N-terminal domain of (Tm^3+)(Ca^2+)[3]-Calmodulin (N60D) are higher than corresponding shifts in C-terminal domain of (Dy^3+/Tm^3+)(Ca^2+)[3]-EhCaBP indicating higher strength of ligand field in parvalbumin and calmodulin when compared with C-terminal domain of EhCaBP. The blue sphere indicates the Ln^3+.

The above figures are reprinted by permission from John Wiley & Sons, Inc.: Proteins (2006, 65, 656-669) copyright 2006.

Figures were selected by an automated process.