PDBsum entry 1dex

Hydrolase

PDB id: 1dex

Contents

Protein chain

233 a.a. *

Ligands

NAG-NAG-BMA-MAN-MAN-MAN

NAG

Waters ×306

* Residue conservation analysis

PDB id:

1dex

Name:

Hydrolase

Title:

Rhamnogalacturonan acetylesterase from aspergillus aculeatus at 1.9 a resolution

Structure:

Rhamnogalacturonan acetylesterase. Chain: a. Engineered: yes

Source:

Aspergillus aculeatus. Organism_taxid: 5053. Strain: ksm 510. Expressed in: aspergillus oryzae. Expression_system_taxid: 5062.

Resolution:

1.90Å R-factor: 0.162 R-free: 0.218

Authors:

A.Molgaard,S.Kauppinen,S.Larsen

Key ref:

A.Mølgaard et al. (2000). Rhamnogalacturonan acetylesterase elucidates the structure and function of a new family of hydrolases. Structure, 8, 373-383. PubMed id: 10801485 DOI: 10.1016/S0969-2126(00)00118-0

Date:

16-Nov-99 Release date: 26-Apr-00

Protein chain

Q00017  (RHA1_ASPAC) -  Rhamnogalacturonan acetylesterase from Aspergillus aculeatus

Seq: 250 a.a.

Struc: 233 a.a.

Enzyme reactions

• Enzyme class: E.C.3.1.1.86 - rhamnogalacturonan acetylesterase.

DOI no: 10.1016/S0969-2126(00)00118-0

Structure 8:373-383 (2000)

PubMed id: 10801485

Rhamnogalacturonan acetylesterase elucidates the structure and function of a new family of hydrolases.

A.Mølgaard, S.Kauppinen, S.Larsen.

ABSTRACT

BACKGROUND: The complex polysaccharide rhamnogalacturonan constitutes a major part of the hairy region of pectin. It can have different types of carbohydrate sidechains attached to the rhamnose residues in the backbone of alternating rhamnose and galacturonic acid residues; the galacturonic acid residues can be methylated or acetylated. Aspergillus aculeatus produces enzymes that are able to perform a synergistic degradation of rhamnogalacturonan. The deacetylation of the backbone by rhamnogalacturonan acetylesterase (RGAE) is an essential prerequisite for the subsequent action of the enzymes that cleave the glycosidic bonds. RESULTS: The structure of RGAE has been determined at 1.55 A resolution. RGAE folds into an alpha/beta/alpha structure. The active site of RGAE is an open cleft containing a serine-histidine-aspartic acid catalytic triad. The position of the three residues relative to the central parallel beta sheet and the lack of the nucleophilic elbow motif found in structures possessing the alpha/beta hydrolase fold show that RGAE does not belong to the alpha/beta hydrolase family. CONCLUSIONS: Structural and sequence comparisons have revealed that, despite very low sequence similarities, RGAE is related to seven other proteins. They are all members of a new hydrolase family, the SGNH-hydrolase family, which includes the carbohydrate esterase family 12 as a distinct subfamily. The SGNH-hydrolase family is characterised by having four conserved blocks of residues, each with one completely conserved residue; serine, glycine, asparagine and histidine, respectively. Each of the four residues plays a role in the catalytic function.

Selected figure(s)

Figure 6.
Figure 6. The orientation of the catalytic triad residues with respect to the overall fold. (a) Schematic diagram of the structure of dienelactone hydrolase (PDB accession number 1din) [43], an a/b hydrolase, viewed from the N-terminal side of the central b sheet. The three catalytic residues align roughly parallel to the central b sheet. (b) RGAE viewed from a similar orientation. The catalytic residues align almost perpendicular to the central b sheet. The figure was prepared using the program MOLSCRIPT [42].

The above figure is reprinted by permission from Cell Press: Structure (2000, 8, 373-383) copyright 2000.

Figure was selected by an automated process.