PDBsum entry 1so0

Isomerase

PDB id: 1so0

Contents

Protein chain

344 a.a. *

Ligands

GAL ×4

Waters ×406

* Residue conservation analysis

PDB id:

1so0

Name:

Isomerase

Title:

Crystal structure of human galactose mutarotase complexed with galactose

Structure:

Aldose 1-epimerase. Chain: a, b, c, d. Synonym: galactose mutarotase. Engineered: yes

Source:

Homo sapiens. Human. Organism_taxid: 9606. Gene: galm. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

2.30Å R-factor: 0.169 R-free: 0.198

Authors:

J.B.Thoden,D.J.Timson,R.J.Reece,H.M.Holden

Key ref:

J.B.Thoden et al. (2004). Molecular structure of human galactose mutarotase. J Biol Chem, 279, 23431-23437. PubMed id: 15026423 DOI: 10.1074/jbc.M402347200

Date:

12-Mar-04 Release date: 30-Mar-04

Protein chains

Q96C23  (GALM_HUMAN) -  Galactose mutarotase from Homo sapiens

Seq: 342 a.a.

Struc: 344 a.a.

Enzyme reactions

• Enzyme class: E.C.5.1.3.3 - aldose 1-epimerase.
• Reaction: alpha-D-glucose = beta-D-glucose

alpha-D-glucose (Bound ligand (Het Group name = GAL) corresponds exactly) = beta-D-glucose

Molecule diagrams generated from .mol files obtained from the KEGG ftp site

Added reference

DOI no: 10.1074/jbc.M402347200

J Biol Chem 279:23431-23437 (2004)

PubMed id: 15026423

Molecular structure of human galactose mutarotase.

J.B.Thoden, D.J.Timson, R.J.Reece, H.M.Holden.

ABSTRACT

Galactose mutarotase catalyzes the conversion of beta-d-galactose to alpha-d-galactose during normal galactose metabolism. The enzyme has been isolated from bacteria, plants, and animals and is present in the cytoplasm of most cells. Here we report the x-ray crystallographic analysis of human galactose mutarotase both in the apoform and complexed with its substrate, beta-d-galactose. The polypeptide chain folds into an intricate array of 29 beta-strands, 25 classical reverse turns, and 2 small alpha-helices. There are two cis-peptide bonds at Arg-78 and Pro-103. The sugar ligand sits in a shallow cleft and is surrounded by Asn-81, Arg-82, His-107, His-176, Asp-243, Gln-279, and Glu-307. Both the side chains of Glu-307 and His-176 are in the proper location to act as a catalytic base and a catalytic acid, respectively. These residues are absolutely conserved among galactose mutarotases. To date, x-ray models for three mutarotases have now been reported, namely that described here and those from Lactococcus lactis and Caenorhabditis elegans. The molecular architectures of these enzymes differ primarily in the loop regions connecting the first two beta-strands. In the human protein, there are six extra residues in the loop compared with the bacterial protein for an approximate longer length of 9 A. In the C. elegans protein, the first 17 residues are missing, thereby reducing the total number of beta-strands by one.

Selected figure(s)

Figure 2.
FIG. 2. Structure of human galactose mutarotase. A ribbon representation of the three-dimensional architecture exhibited by the apoenzyme is shown in a. For clarity, only the major strands of the -sheet are displayed. Asterisks indicate the positions of cis-Arg-78 and cis-Pro-103. The location of the active site is depicted in b as a space-filling representation. Note that the 3-, 4-, and 6-hydroxyl groups of galactose, from left to right and indicated by the red spheres, are solvent-exposed. The view is approximately the same as displayed in a.

Figure 3.
FIG. 3. The active site for human galactose mutarotase. A close-up stereo view of those amino acid residues involved in sugar binding is displayed in a. The color coding for the ribbon representation is the same as in Fig. 2. The sugar is highlighted in grayish bonds. Possible hydrogen bonding interactions between the protein and the ligand are shown schematically in b. The dotted lines indicate distances equal to or below 3.2 Å.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2004, 279, 23431-23437) copyright 2004.

Figures were selected by an automated process.