2O1G

Natural occurring mutant of Human ABO(H) Galactosyltransferase: GTB/M214T

Summary for 2O1G

• Entry DOI: 10.2210/pdb2o1g/pdb
• Related: 2O1F
• Descriptor: ABO glycosyltransferase, MERCURY (II) ION (3 entities in total)
• Functional Keywords: glycosyltransferase, gtb, blood type subgroups, naturally occuring mutant, dxd, transferase
• Biological source: Homo sapiens (human)
• Total number of polymer chains: 1
• Total formula weight: 35499.70

Authors

Letts, J.A.,Borisova, S.N.,Evans, S.V. (deposition date: 2006-11-28, release date: 2007-02-06, Last modification date: 2023-08-30)

Primary citation

Persson, M.,Letts, J.A.,Hosseini-Maaf, B.,Borisova, S.N.,Palcic, M.M.,Evans, S.V.,Olsson, M.L.
Structural effects of naturally occurring human blood group B galactosyltransferase mutations adjacent to the DXD motif.
J.Biol.Chem., 282:9564-9570, 2007

PubMed Abstract: Human blood group A and B antigens are produced by two closely related glycosyltransferase enzymes. An N-acetylgalactosaminyltransferase (GTA) utilizes UDP-GalNAc to extend H antigen acceptors (Fuc alpha(1-2)Gal beta-OR) producing A antigens, whereas a galactosyltransferase (GTB) utilizes UDP-Gal as a donor to extend H structures producing B antigens. GTA and GTB have a characteristic (211)DVD(213) motif that coordinates to a Mn(2+) ion shown to be critical in donor binding and catalysis. Three GTB mutants, M214V, M214T, and M214R, with alterations adjacent to the (211)DVD(213) motif have been identified in blood banking laboratories. From serological phenotyping, individuals with the M214R mutation show the B(el) variant expressing very low levels of B antigens, whereas those with M214T and M214V mutations give rise to A(weak)B phenotypes. Kinetic analysis of recombinant mutant GTB enzymes revealed that M214R has a 1200-fold decrease in k(cat) compared with wild type GTB. The crystal structure of M214R showed that DVD motif coordination to Mn(2+) was disrupted by Arg-214 causing displacement of the metal by a water molecule. Kinetic characterizations of the M214T and M214V mutants revealed they both had GTA and GTB activity consistent with the serology. The crystal structure of the M214T mutant showed no change in DVD coordination to Mn(2+). Instead a critical residue, Met-266, which is responsible for determining donor specificity, had adopted alternate conformations. The conformation with the highest occupancy opens up the active site to accommodate the larger A-specific donor, UDP-GalNAc, accounting for the dual specificity.

PubMed: 17259183
DOI: 10.1074/jbc.M610998200

Experimental method

X-RAY DIFFRACTION (1.71 Å)