PDBsum entry 1clm

Calcium-binding protein

PDB id: 1clm

Contents

Protein chain

144 a.a. *

Metals

_CA ×4

Waters ×71

* Residue conservation analysis

PDB id:

1clm

Name:

Calcium-binding protein

Title:

Structure of paramecium tetraurelia calmodulin at 1.8 angstroms resolution

Structure:

Calmodulin. Chain: a. Engineered: yes

Source:

Paramecium tetraurelia. Organism_taxid: 5888

Resolution:

1.80Å R-factor: 0.210

Authors:

M.Sundaralingam

Key ref:

S.T.Rao et al. (1993). Structure of Paramecium tetraurelia calmodulin at 1.8 A resolution. Protein Sci, 2, 436-447. PubMed id: 8453381 DOI: 10.1002/pro.5560020316

Date:

23-Jan-93 Release date: 31-Oct-93

Protein chain

P07463  (CALM_PARTE) -  Calmodulin from Paramecium tetraurelia

Seq: 149 a.a.

Struc: 144 a.a.

DOI no: 10.1002/pro.5560020316

Protein Sci 2:436-447 (1993)

PubMed id: 8453381

Structure of Paramecium tetraurelia calmodulin at 1.8 A resolution.

S.T.Rao, S.Wu, K.A.Satyshur, K.Y.Ling, C.Kung, M.Sundaralingam.

ABSTRACT

The crystal structure of calmodulin (CaM; M(r) 16,700, 148 residues) from the ciliated protozoan Paramecium tetraurelia (PCaM) has been determined and refined using 1.8 A resolution area detector data. The crystals are triclinic, space group P1, a = 29.66, b = 53.79, c = 25.49 A, alpha = 92.84, beta = 97.02, and gamma = 88.54 degrees with one molecule in the unit cell. Crystals of the mammalian CaM (MCaM; Babu et al., 1988) and Drosophila CaM (DCaM; Taylor et al., 1991) also belong to the same space group with very similar cell dimensions. All three CaMs have 148 residues, but there are 17 sequence changes between PCaM and MCaM and 16 changes between PCaM and DCaM. The initial difference in the molecular orientation between the PCaM and MCaM crystals was approximately 7 degrees as determined by the rotation function. The reoriented Paramecium model was extensively refitted using omit maps and refined using XPLOR. The R-value for 11,458 reflections with F > 3 sigma is 0.21, and the model consists of protein atoms for residues 4-147, 4 calcium ions, and 71 solvent molecules. The root mean square (rms) deviations in the bond lengths and bond angles in the model from ideal values are 0.016 A and 3 degrees, respectively. The molecular orientation of the final PCaM model differs from MCaM by only 1.7 degrees. The overall Paramecium CaM structure is very similar to the other calmodulin structures with a seven-turn long central helix connecting the two terminal domains, each containing two Ca-binding EF-hand motifs. The rms deviation in the backbone N, Ca, C, and O atoms between PCaM and MCaM is 0.52 A and between PCaM and DCaM is 0.85 A. The long central helix regions differ, where the B-factors are also high, particularly in PCaM and MCaM. Unlike the MCaM structure, with one kink at D80 in the middle of the linker region, and the DCaM structure, with two kinks at K75 and I85, in our PCaM structure there are no kinks in the helix; the distortion appears to be more gradually distributed over the entire helical region, which is bent with an apparent radius of curvature of 74.5(2) A. The different distortions in the central helical region probably arise from its inherent mobility.

Selected figure(s)

Figure 1.
Fig. 1. Theprimarysequnce of mammalianCaM (top line)iscompared withParameciumCaM(middleline)and rosophila CaM (bottomline). Residuesthatare common withmammalianCaMareindicated by -. Thehelicaland calcium-binding sites aremarkedandthe loo residues involved n calcium bindingaremarkedwith *,

Figure 2.
Fig. 2. Ribbondiagram (Priestle, 1988) of PCaM. The helicalregions A through H remarked, as ell as thetermini.

The above figures are reprinted from an Open Access publication published by the Protein Society: Protein Sci (1993, 2, 436-447) copyright 1993.

Figures were selected by an automated process.