PDBsum entry 2rj4

Transferase

PDB id: 2rj4

Contents

Protein chain

290 a.a. *

Ligands

UDP

AD7

Metals

_MN

Waters ×230

* Residue conservation analysis

PDB id:

2rj4

Name:

Transferase

Title:

B-specific alpha-1,3-galactosyltransferase \ g176r +udp+ada

Structure:

Glycoprotein-fucosylgalactoside alpha- galactosyltransferase. Chain: a. Synonym: fucosylglycoprotein 3-alpha- galactosyltransferase, histo- blood group b transferase, b transferase. Engineered: yes

Source:

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

Resolution:

1.47Å R-factor: 0.207 R-free: 0.226

Authors:

S.V.Evans,J.A.Alfaro

Key ref:

J.A.Alfaro et al. (2008). ABO(H) blood group A and B glycosyltransferases recognize substrate via specific conformational changes. J Biol Chem, 283, 10097-10108. PubMed id: 18192272 DOI: 10.1074/jbc.M708669200

Date:

14-Oct-07 Release date: 05-Feb-08

Protein chain

P16442  (BGAT_HUMAN) -  Histo-blood group ABO system transferase from Homo sapiens

Seq: 354 a.a.

Struc: 290 a.a.*

* PDB and UniProt seqs differ at 5 residue positions (black crosses)

Enzyme reactions

• Enzyme class 1: E.C.2.4.1.37 - fucosylgalactoside 3-alpha-galactosyltransferase.
• Reaction: an alpha-L-fucosyl-(1->2)-beta-D-galactosyl derivative + UDP-alpha-D- galactose = an alpha-D-galactosyl-(1->3)-[alpha-L-fucosyl-(1->2)]-beta-D- galactosyl derivative + UDP + H⁺

alpha-L-fucosyl-(1->2)-beta-D-galactosyl derivative + UDP-alpha-D- galactose = alpha-D-galactosyl-(1->3)-[alpha-L-fucosyl-(1->2)]-beta-D- galactosyl derivative + UDP + H(+) (Bound ligand (Het Group name = UDP) corresponds exactly)

• Enzyme class 2: E.C.2.4.1.40 - glycoprotein-fucosylgalactoside alpha-N-acetylgalactosaminyltransferase.
• Reaction: an alpha-L-fucosyl-(1->2)-beta-D-galactosyl derivative + UDP-N-acetyl- alpha-D-galactosamine = an N-acetyl-alpha-D-galactosaminyl-(1->3)-[alpha- L-fucosyl-(1->2)]-beta-D-galactosyl derivative + UDP + H⁺

alpha-L-fucosyl-(1->2)-beta-D-galactosyl derivative + UDP-N-acetyl- alpha-D-galactosamine = N-acetyl-alpha-D-galactosaminyl-(1->3)-[alpha- L-fucosyl-(1->2)]-beta-D-galactosyl derivative + UDP + H(+) (Bound ligand (Het Group name = UDP) corresponds exactly)

Note, where more than one E.C. class is given (as above), each may correspond to a different protein domain or, in the case of polyprotein precursors, to a different mature protein.

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

Added reference

DOI no: 10.1074/jbc.M708669200

J Biol Chem 283:10097-10108 (2008)

PubMed id: 18192272

ABO(H) blood group A and B glycosyltransferases recognize substrate via specific conformational changes.

J.A.Alfaro, R.B.Zheng, M.Persson, J.A.Letts, R.Polakowski, Y.Bai, S.N.Borisova, N.O.Seto, T.L.Lowary, M.M.Palcic, S.V.Evans.

ABSTRACT

The final step in the enzymatic synthesis of the ABO(H) blood group A and B antigens is catalyzed by two closely related glycosyltransferases, an alpha-(1-->3)-N-acetylgalactosaminyltransferase (GTA) and an alpha-(1-->3)-galactosyltransferase (GTB). Of their 354 amino acid residues, GTA and GTB differ by only four "critical" residues. High resolution structures for GTB and the GTA/GTB chimeric enzymes GTB/G176R and GTB/G176R/G235S bound to a panel of donor and acceptor analog substrates reveal "open," "semi-closed," and "closed" conformations as the enzymes go from the unliganded to the liganded states. In the open form the internal polypeptide loop (amino acid residues 177-195) adjacent to the active site in the unliganded or H antigen-bound enzymes is composed of two alpha-helices spanning Arg(180)-Met(186) and Arg(188)-Asp(194), respectively. The semi-closed and closed forms of the enzymes are generated by binding of UDP or of UDP and H antigen analogs, respectively, and show that these helices merge to form a single distorted helical structure with alternating alpha-3(10)-alpha character that partially occludes the active site. The closed form is distinguished from the semi-closed form by the ordering of the final nine C-terminal residues through the formation of hydrogen bonds to both UDP and H antigen analogs. The semi-closed forms for various mutants generally show significantly more disorder than the open forms, whereas the closed forms display little or no disorder depending strongly on the identity of residue 176. Finally, the use of synthetic analogs reveals how H antigen acceptor binding can be critical in stabilizing the closed conformation. These structures demonstrate a delicately balanced substrate recognition mechanism and give insight on critical aspects of donor and acceptor specificity, on the order of substrate binding, and on the requirements for catalysis.

Selected figure(s)

Figure 1.
FIGURE 1. Conformational changes associated with substrate binding. a, superimposition of unliganded ABBB in the open form (white) with AABB+UDP-Gal+DA in the closed form (yellow/red) showing the internal and C-terminal loops (red), UDP-Gal and DA (orange), and Mn^2+ (blue), and the location of Arg^176. b, expanded view about the active site with an arrow indicating the movement of the internal loop toward the donor in going from the open state to both the semi-closed or closed states, and showing the ordering of the C-terminal residues to form the closed state. c, stereoview of electron density corresponding to the internal loop in AABB+UDP showing two distinct conformations of the enzyme (at 50% occupancy) corresponding to the open (yellow) and semi-closed (green) forms of the enzyme. The disorder converges at Met^189 (gray). d, the transformation of the internal loop (residues 176-195) from the open (left) to the semi-closed (right) conformation is accomplished by the merger of two -helices (Arg^180-Met^186 and Arg^187-Asp^194) into a distorted helical structure with alternating -3[10]- character. The pivot point is indicated by a star.

Figure 4.
FIGURE 4. Schematic representation of donor and acceptor recognition in GTB. The chimeric enzyme AABB displays the closed form when bound to UDP-Gal and DA, which allows for a complete characterization of substrate recognition. The acceptor Gal-O-3 is modeled and does not appear in the 3-deoxy acceptor DA.

The above figures are reprinted by permission from the ASBMB: J Biol Chem (2008, 283, 10097-10108) copyright 2008.

Figures were selected by the author.