Identification and characterization of three novel beta 1,3-N-acetylglucosaminyltransferases structurally related to the beta 1,3-galactosyltransferase family.
We have isolated three types of cDNAs encoding novel beta1,3-N-acetylglucosaminyltransferases (designated beta3Gn-T2, -T3, and -T4) from human gastric mucosa and the neuroblastoma cell line SK-N-MC. These enzymes are predicted to be type 2 transmembrane proteins of 397, 372, and 378 amino acids, respectively. They share motifs conserved among members of the beta1,3-galactosyltransferase family and a beta1,3-N-acetylglucosaminyltransferase (designated beta3Gn-T1), but show no structural similarity to another type of beta1,3-N-acetylglucosaminyltransferase (iGnT). Each of the enzymes expressed by insect cells as a secreted protein fused to the FLAG peptide showed beta1,3-N-acetylglucosaminyltransferase activity for type 2 oligosaccharides but not beta1,3-galactosyltransferase activity. These enzymes exhibited different substrate specificity. Transfection of Namalwa KJM-1 cells with beta3Gn-T2, -T3, or -T4 cDNA led to an increase in poly-N-acetyllactosamines recognized by an anti-i-antigen antibody or specific lectins. The expression profiles of these beta3Gn-Ts were different among 35 human tissues. beta3Gn-T2 was ubiquitously expressed, whereas expression of beta3Gn-T3 and -T4 was relatively restricted. beta3Gn-T3 was expressed in colon, jejunum, stomach, esophagus, placenta, and trachea. beta3Gn-T4 was mainly expressed in brain. These results have revealed that several beta1,3-N-acetylglucosaminyltransferases form a family with structural similarity to the beta1,3-galactosyltransferase family. Considering the differences in substrate specificity and distribution, each beta1,3-N-acetylglucosaminyltransferase may play different roles.
Shiraishi
N
N
Tokyo Research Laboratories, Kyowa Hakko Kogyo Company, Limited, 3-6-6 Asahi-machi, Machida-shi, Tokyo 194-8533, Japan.
Natsume
A
A
Togayachi
A
A
Endo
T
T
Akashima
T
T
Yamada
Y
Y
Imai
N
N
Nakagawa
S
S
Koizumi
S
S
Sekine
S
S
Narimatsu
H
H
Sasaki
K
K
D000595:Amino Acid Sequence; D000818:Animals; D002461:Cell Line, Transformed; D002478:Cells, Cultured; D005700:Galactosyltransferases / Q000737:chemistry*; D006801:Humans; D007313:Insecta; D008969:Molecular Sequence Data; D017351:N-Acetylglucosaminyltransferases / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D010802:Phylogeny; D011134:Polysaccharides / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution
D011134:Polysaccharides; D012333:RNA, Messenger; C037199:poly-N-acetyllactosamine; D005700:Galactosyltransferases; D017351:N-Acetylglucosaminyltransferases; C428134:beta--1,3-N-acetylglucosaminyltransferase T4; C428133:beta-1,3-N--acetylglucosaminyltransferase T3; C428132:B3GNT2 protein, human