PDBsum entry: 1c9o

Transcription

PDB id: 1c9o

Contents

Protein chains

66 a.a. *

Ligands

TRS ×3

Metals

_NA ×2

Waters ×274

* Residue conservation analysis

PDB id:

1c9o

Name:

Transcription

Title:

Crystal structure analysis of the bacillus caldolyticus cold shock protein bc-csp

Structure:

Cold-shock protein. Chain: a, b. Synonym: cspb

Source:

Bacillus caldolyticus. Organism_taxid: 1394

Resolution:

1.17Å R-factor: 0.125 R-free: 0.179

Authors:

U.Mueller,D.Perl,F.X.Schmid,U.Heinemann

Key ref:

U.Mueller et al. (2000). Thermal stability and atomic-resolution crystal structure of the Bacillus caldolyticus cold shock protein. J Mol Biol, 297, 975-988. PubMed id: 10736231 DOI: 10.1006/jmbi.2000.3602

Date:

03-Aug-99 Release date: 02-Apr-00

Protein chains

P41016  (CSPB_BACCL) -  Cold shock protein CspB

Seq: 66 a.a.

Struc: 66 a.a.

 Gene Ontology (GO) functional annotation 

• Cellular component: cytoplasm (1 term)
• Biological process: response to stress (4 terms)
• Biochemical function: nucleic acid binding (2 terms)

DOI no: 10.1006/jmbi.2000.3602

J Mol Biol 297:975-988 (2000)

PubMed id: 10736231

Thermal stability and atomic-resolution crystal structure of the Bacillus caldolyticus cold shock protein.

U.Mueller, D.Perl, F.X.Schmid, U.Heinemann.

ABSTRACT

The bacterial cold shock proteins are small compact beta-barrel proteins without disulfide bonds, cis-proline residues or tightly bound cofactors. Bc-Csp, the cold shock protein from the thermophile Bacillus caldolyticus shows a twofold increase in the free energy of stabilization relative to its homolog Bs-CspB from the mesophile Bacillus subtilis, although the two proteins differ by only 12 out of 67 amino acid residues. This pair of cold shock proteins thus represents a good system to study the atomic determinants of protein thermostability. Bs-CspB and Bc-Csp both unfold reversibly in cooperative transitions with T(M) values of 49.0 degrees C and 77.3 degrees C, respectively, at pH 7.0. Addition of 0.5 M salt stabilizes Bs-CspB but destabilizes Bc-Csp. To understand these differences at the structural level, the crystal structure of Bc-Csp was determined at 1.17 A resolution and refined to R=12.5% (R(free)=17.9%). The molecular structures of Bc-Csp and Bs-CspB are virtually identical in the central beta-sheet and in the binding region for nucleic acids. Significant differences are found in the distribution of surface charges including a sodium ion binding site present in Bc-Csp, which was not observed in the crystal structure of the Bs-CspB. Electrostatic interactions are overall favorable for Bc-Csp, but unfavorable for Bs-CspB. They provide the major source for the increased thermostability of Bc-Csp. This can be explained based on the atomic-resolution crystal structure of Bc-Csp. It identifies a number of potentially stabilizing ionic interactions including a cation-binding site and reveals significant changes in the electrostatic surface potential.

Selected figure(s)

Figure 2.
Figure 2. Thermal unfolding transitions of Bs-CspB (0m, T[M] = 49.0 °C) and Bc-Csp ( o , T[M] = 77.3 °C) in 5 mM sodium cacodylate-HCl (pH 7.0) at protein concentrations of 4 µM. The transitions were monitored by the decrease of the CD signal at 222.6 nm and 1 cm pathlength. The heating rate was 30 °C/hour. The fractions of native protein as obtained after a two-state analysis of the data are shown as a function of temperature. The results of the analysis based on a two-state model [Mayr et al 1993] is shown by the continuous lines. For the analysis the heat capacity change DC[P] of unfolding was assumed to be 4000 J·mol -1·K -1.

Figure 7.
Figure 7. Surface charge of Bc-Csp-A and Bs-CspB. Surface charges were calculated by DELPHI [Nicholls et al 1991] using the major conformer for residues with multiple conformations and standard rotamer settings for those disordered side-chains that are not included in the crystallographic models. Fully charged residues Asp, Glu, Arg and Lys and terminal amino and carboxy functions were assumed, and the ionic strength of the surrounding solvent sphere was set to 145 mM. The surfaces were generated with GRASP [Nicholls et al 1991] using a probe radius of 1.4 Å and colored using the DELPHI electrostatic potential maps. Potentials of -10 kT/e or less are shown in red, neutral potential (0 kT/e) is colorless, and potentials of +10 kT/e or more are colored blue. Molecules in the bottom row are rotated by 180 ° around the vertical axis with respect to the top row. The presumed nucleic acid binding surface is to the right in the top row of images. Schematic drawings in the left and rightmost columns identify the charged residues that give rise to the electrostatic surface potential. Charged residues are labeled if they differ between Bc-Csp and Bs-CspB or are referred to in the text.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2000, 297, 975-988) copyright 2000.

Figures were selected by the author.