Molecule of the Month: ABO Blood Type Glycosyltransferases
ABO blood types are determined by an enzyme that attaches sugars to proteins
What's Your Type?
Binding Blood Carbohydrates
Exploring the Structure
Glycosyltransferases GTA and GTB (PDB entries 1lzi and 3i0g)
The ABO blood type of each person is determined by a single gene. For the A type, there is a gene for GTA, a glycosyltransferase that adds N-acetylgalactosamine. For type B, the gene encodes GTB, a different glycosyltransferase that adds galactose. For type O, neither enzyme is made. Amazingly, GTA and GTB are almost identical, with only four amino acid changes (shown here in turquoise on PDB entry 1lzi ). This tiny difference in sequence, however, has life-or-death consequences! To explore the structure of these two enzymes, click on the image for an interactive Jmol.
Topics for Further Discussion
- Researchers have studied the specificity of GTA and GTB by creating mutants that include some amino acids from GTA and some from GTB. Structures of many of these hybrid glycosyltransferases are included in the PDB.
- The PDB includes many proteins involved with other blood types--try searching for "Blood Group Antigens" to explore some of them.
Related PDB-101 Resources
- Browse You and Your Health
- Browse Enzymes
- J. Koscielak (2001) ABH blood group active glycoconjugates from human red cells. Transfusion Medicine 11, 267-279.
- S. I. Patenaude, N. O. L. Seto, S. N. Borisova, A. Szpacenko, S. L. Marcus, M. M. Palcic & S. V. Evans (2002) The structural basis for specificity in human ABO(H) blood group biosynthesis. Nature Structural Biology 9, 685-690.
December 2012, David Goodsellhttp://doi.org/10.2210/rcsb_pdb/mom_2012_12