© 2006 The Japanese Biochemical Society.
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Analysis of Sialyltransferase-Like Proteins from Oryza sativa



1 Cellular Biochemistry Laboratory and 2 Plant Functions Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198; 3 Plant Biotechnology Department, National Institute of Agrobiological Sciences, 2-1-2 Kannondai, Tsukuba, Ibaraki 305-8602; 4 Plant Molecular Biology Laboratory, RIKEN Tsukuba Institute, 3-1-1 Koyadai, Tsukuba, Ibaraki 305-0074; and 5 Future Science and Technology Joint Research Center, Institute of Glycotechnology, Tokai University, 1117 Kitakaname, Hiratsuka, Kanagawa 259-1292
¶ To whom correspondence should be addressed. Tel: +81-48-467-9616, Fax: +81-48-467-9617, E-mail: staka{at}riken.jp
Sialic acids are widely distributed among living creatures, from bacteria to mammals, but it has been commonly accepted that they do not exist in plants. However, with the progress of genome analyses, putative gene homologs of animal sialyltransferases have been detected in the genome of some plants. In this study, we cloned three genes from Oryza sativa (Japanese rice) that encode sialyltransferase-like proteins, designated OsSTLP1, 2, and 3, and analyzed the enzymatic activity of the proteins. OsSTLP1, 2, and 3 consist of 393, 396, and 384 amino acids, respectively, and each contains sequences similar to the sialyl motifs that are highly conserved among animal sialyltransferases. The recombinant soluble forms of OsSTLPs produced by COS-7 cells were analyzed for sialyltransferase-like activity. OsSTLP1 exhibited such activity toward the oligosaccharide Galß1,4GlcNAc and such glycoproteins as asialofetuin,
1-acid glycoprotein, and asialo-
1-acid glycoprotein; OsSTLP3 exhibited similar activity toward asialofetuin; and OsSTLP2 exhibited no sialyltransferase-like activity. The sialic acid transferred by OsSTLP1 or 3 was linked to galactose of Galß1,4GlcNAc through
2,6-linkage. This is the first report of plant proteins having sialyltransferase-like activity.
* Present address: Glyco-chain Functions Laboratory, RIKEN-FRS, 2-1 Hirosawa, Wako, Saitama 351-0198.
Present address: Accelerator Research Program, Application and Development Group, RIKEN-FRS, 2-1 Hirosawa, Wako, Saitama 351-0198.
Present address: Plant Science Center, RIKEN, 1-7-22 Suehiro, Tsurumi, Yokohama 230-0045.
Present address: Antibiotics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198.
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