Expression cloning of a new member of the ABO blood group glycosyltransferases, iGb3 synthase, that directs the synthesis of isoglobo-glycosphingolipids.
The large array of different glycolipids described in mammalian tissues is a reflection, in part, of diverse glycosyltransferase expression. Herein, we describe the cloning of a UDP-galactose: beta-d-galactosyl-1,4-glucosylceramide alpha-1, 3-galactosyltransferase (iGb(3) synthase) from a rat placental cDNA expression library. iGb(3) synthase acts on lactosylceramide, LacCer (Galbeta1,4Glcbeta1Cer) to form iGb(3) (Galalpha1,3Galbeta1, 4Glcbeta1Cer) initiating the synthesis of the isoglobo-series of glycosphingolipids. The isolated cDNA encoded a predicted protein of 339 amino acids, which shows extensive homology (40-50% identity) to members of the ABO gene family that includes: murine alpha1, 3-galactosyltransferase, Forssman (Gb(5)) synthase, and the ABO glycosyltransferases. In contrast to the murine alpha1, 3-galactosyltransferase, iGb(3) synthase preferentially modifies glycolipids over glycoprotein substrates. Reverse transcriptase-polymerase chain reaction revealed a widespread tissue distribution of iGb(3) synthase RNA expression, with high levels observed in spleen, thymus, and skeletal muscle. As an indirect consequence of the expression cloning strategy used, we have been able to identify several potential glycolipid biosynthetic pathways where iGb(3) functions, including the globo- and isoglobo-series of glycolipids.
Keusch
J J
JJ
Department of Pathology, Washington University School of Medicine, St. Louis, MO 63110, USA. jkeusch@pathbox.wustl.edu
Manzella
S M
SM
Nyame
K A
KA
Cummings
R D
RD
Baenziger
J U
JU
D000017:ABO Blood-Group System / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry; D001483:Base Sequence; D016466:CHO Cells; D002469:Cell Separation; D002855:Chromatography, Thin Layer; D003001:Cloning, Molecular; D006224:Cricetinae; D018076:DNA, Complementary / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D005700:Galactosyltransferases / Q000235:genetics* / Q000502:physiology*; D015723:Gene Library; D005915:Globosides / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000378:metabolism; D006028:Glycosphingolipids / Q000096:biosynthesis*; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010920:Placenta / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity; D014018:Tissue Distribution; D014162:Transfection
D000017:ABO Blood-Group System; D000911:Antibodies, Monoclonal; D018076:DNA, Complementary; D005915:Globosides; D006028:Glycosphingolipids; C037097:isoglobotriaosylceramide; D005700:Galactosyltransferases; C413211:UDP-galactose beta-D-galactosyl-1,4-glycosylceramide alpha-1,3-galactosyltransferase; C045097:UDP-galactose-lactosylceramide alpha 1-4-galactosyltransferase; D006026:Glycoside Hydrolases