Glycobiology Advance Access originally published online on September 16, 2008
Glycobiology 2008 18(12):1065-1073; doi:10.1093/glycob/cwn089
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Functional and structural bases of a cysteine-less mutant as a long-lasting substitute for galectin-1
2 Department of Endocrinology, Faculty of Medicine
3 Division of Structural Biology, Life Science Research Center, Kagawa University, Kagawa 761-0793
4 Research Center for Medical Glycoscience, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 2, 1-1-1, Umezono, Tsukuba, Ibaraki 305-8568
5 GalPharma Co., Ltd., 2217-44 Hayashimachi, Takamatsu, Kagawa 761-0301, Japan
1 To whom correspondence should be addressed: Tel: +81-87-891-2107; Fax: +81-87-891-2108; e-mail: nnishi{at}med.kagawa-u.ac.jp
Received on April 24, 2008; revised on September 12, 2008; accepted on September 12, 2008
Galectin-1 (Gal-1), a member of the β-galactoside-binding animal lectin family, has a wide range of biological activities, which makes it an attractive target for medical applications. Unlike other galectins, Gal-1 is susceptible to oxidation at cysteine residues, which is troublesome for in vitro/vivo studies. To overcome this problem, we prepared a cysteine-less mutant of Gal-1 (CSGal-1) by substituting all cysteine residues with serine residues. In the case of wild-type Gal-1, the formation of covalent dimers/oligomers was evident after 10 days of storage in the absence of a reducing agent with a concomitant decrease in hemagglutination activity, while CSGal-1 did not form multimers and retained full hemagglutination activity after 400 days of storage. Frontal affinity chromatography showed that the sugar-binding specificity and affinity of Gal-1 for model glycans were barely affected by the mutagenesis. Gal-1 is known to induce cell signaling leading to an increase in the intracytoplasmic calcium concentration and to cell death. CSGal-1 is also capable of inducing calcium flux and growth inhibition in Jurkat cells, which are comparable to or more potent than those induced by Gal-1. The X-ray structure of the CSGal-1/lactose complex has been determined. The structure of CSGal-1 is almost identical to that of wild-type human Gal-1, showing that the amino acid substitutions do not affect the overall structure or carbohydrate-binding site structure of the protein. These results indicate that CSGal-1 can serve as a stable substitute for Gal-1.
Key words: galectin / site-directed mutagenesis / thiol oxidation / X-ray crystallography