PDBsum entry: 1tvn

Hydrolase

PDB-id: 1tvn

Biological unit* = asymmetric unit,
as shown
(*as deduced by PQS)

Contents

Description

Header details

Header records

References

PROCHECK

Protein chains

293 a.a. *

Waters ×776

* Residue conservation analysis

Tools

Clefts Calculation

PDB id:

1tvn

Name:

Hydrolase

Title:

Cellulase cel5g from pseudoalteromonas haloplanktis, a family gh 5-2 enzyme

Structure:

Cellulase. Chain: a, b. Fragment: catalytic domain. Synonym: endoglucanase g. Engineered: yes

Source:

Pseudoalteromonas haloplanktis. Organism_taxid: 228. Gene: celg. Expressed in: escherichia coli. Expression_system_taxid: 562.

Biological unit:

Dimer (from PQS)

UniProt:

Chains A, B: O86099 (O86099_PSEHA)

Seq:

Struc:

Seq:

494 a.a.

Struc:

293 a.a.

Key:	PfamA domain
Secondary structure	CATH domain

Enzyme class:

E.C.3.2.1.4   [IntEnz]   [ExPASy]   [KEGG]   [BRENDA]

Reaction:

Endohydrolysis of 1,4-beta-D-glucosidic linkages in cellulose, lichenin and cereal beta-D-glucans.

Resolution:

1.41Å

R-factor:

0.150

R-free:

0.177

Authors:

S.Violot,R.Haser,N.Aghajari

Key ref:

S.Violot et al. (2005). Structure of a full length psychrophilic cellulase from Pseudoalteromonas haloplanktis revealed by X-ray diffraction and small angle X-ray scattering.. J Mol Biol, 348, 1211-1224. [PubMed id: 15854656] [DOI: 10.1016/j.jmb.2005.03.026]

Date:

30-Jun-04

Release date:

17-May-05

Related entries:

1tvp
the same protein complexed with cellobiose

Quick_links

Procheck

Clefts

Surface

Key reference

DOI no: 10.1016/j.jmb.2005.03.026

J Mol Biol 348:1211-1224 (2005)

PubMed id: 15854656

Structure of a full length psychrophilic cellulase from Pseudoalteromonas haloplanktis revealed by X-ray diffraction and small angle X-ray scattering.

S.Violot, N.Aghajari, M.Czjzek, G.Feller, G.K.Sonan, P.Gouet, C.Gerday, R.Haser, V.Receveur-Bréchot.

ABSTRACT

Pseudoalteromonas haloplanktis is a psychrophilic Gram-negative bacterium isolated in Antarctica, that lives on organic remains of algae. This bacterium converts the cellulose, highly constitutive of algae, into an immediate nutritive form by biodegrading this biopolymer. To understand the mechanisms of cold adaptation of its enzymatic components, we studied the structural properties of an endoglucanase, Cel5G, by complementary methods, X-ray crystallography and small angle X-ray scattering. Using X-ray crystallography, we determined the structure of the catalytic core module of this family 5 endoglucanase, at 1.4A resolution in its native form and at 1.6A in the cellobiose-bound form. The catalytic module of Cel5G presents the (beta/alpha)(8)-barrel structure typical of clan GH-A of glycoside hydrolase families. The structural comparison of the catalytic core of Cel5G with the mesophilic catalytic core of Cel5A from Erwinia chrysanthemi revealed modifications at the atomic level leading to higher flexibility and thermolability, which might account for the higher activity of Cel5G at low temperatures. Using small angle X-ray scattering we further explored the structure at the entire enzyme level. We analyzed the dimensions, shape, and conformation of Cel5G full length in solution and especially of the linker between the catalytic module and the cellulose-binding module. The results showed that the linker is unstructured, and unusually long and flexible, a peculiarity that distinguishes it from its mesophilic counterpart. Loops formed at the base by disulfide bridges presumably add constraints to stabilize the most extended conformations. These results suggest that the linker plays a major role in cold adaptation of this psychrophilic enzyme, allowing steric optimization of substrate accessibility.

Selected figure(s)

Figure 1.
Figure 1. (a) Stereo view of the superimposition of the catalytic module of Cel5G (blue) on that of Cel5A from E. chrysanthemi (red) catalytic module. The Figure was prepared with MOLSCRIPT60 and BOBSCRIPT.61^ and 62 (b) Sequence comparison of the catalytic modules of Cel5G (blue) with Cel5A E. chrysanthemi (red), respectively. Catalytic residues are indicated (blue font), as well as supplementary residues in Cel5G[CM] versus Cel5A[CM] (golden font). The eight conserved residues in family 5 are indicated (green stars), as well as the three conserved residues in subfamily 5-2 (pink stars). Sequence alignment was performed with the program CLUSTAL62 and color coded with ESPript.63

Figure 6.
Figure 6. (a) Shape calculated with GASBOR (blue) superimposed with ten different models of Cel5G provided by GLOOPY represented by secondary structure element type. (b) C^a trace of a typical linker modelled by GLOOPY exhibiting loops (red) putatively closed by disulfide bonds (yellow). (c) Fit on the experimental scattering curve obtained with the average form factor of the different models provided by GLOOPY.

The above figures are reprinted by permission from Elsevier: J Mol Biol (2005, 348, 1211-1224) copyright 2005.

Figures were selected by the author.