Ogata M, Nakajima M, Kato T, Obara T, Yagi H, Kato K, Usui T, Park EY. Synthesis of sialoglycopolypeptide for potentially blocking influenza virus infection using a rat alpha2,6-sialyltransferase expressed in BmNPV bacmid-injected silkworm larvae.
BMC Biotechnol 2009;
9:54. [PMID:
19500344 PMCID:
PMC3224744 DOI:
10.1186/1472-6750-9-54]
[Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Accepted: 06/05/2009] [Indexed: 11/10/2022] Open
Abstract
Background
Sialic acid is a deoxy uronic acid with a skeleton of nine carbons which is mostly found on cell surface in animals. This sialic acid on cell surface performs various biological functions by acting as a receptor for microorganisms, viruses, toxins, and hormones; by masking receptors; and by regulating the immune system. In order to synthesize an artificial sialoglycoprotein, we developed a large-scale production of rat α2,6-sialyltransferase (ST6Gal1). The ST6Gal1 was expressed in fifth instar silkworm larval hemolymph using recombinant both cysteine protease- and chitinase-deficient Bombyx mori nucleopolyhedrovirus (BmNPV-CP--Chi-) bacmid. The expressed ST6Gal1 was purified, characterized and used for sialylation of asialoglycopolypeptide. We tested the inhibitory effect of the synthesized α2,6-sialoglycopolypeptide on hemagglutination by Sambucus nigra (SNA) lectin.
Results
FLAG-tagged recombinant ST6Gal1 was expressed efficiently and purified by precipitation with ammonium sulphate followed by affinity chromatography on an anti-FLAG M2 column, generating 2.2 mg purified fusion protein from only 11 silkworm larvae, with a recovery yield of 64%. The purified ST6Gal1 was characterized and its N-glycan patterns were found to be approximately paucimannosidic type by HPLC mapping method. Fluorescently-labelled N-acetyllactosamine (LacNAc) glycoside containing dansyl group was synthesized chemo-enzymatically as high-sensitivity acceptor substrate for ST6Gal1. The acceptor substrate specificity of the enzyme was similar to that of rat liver ST6Gal1. The fluorescent glycoside is useful as a substrate for a highly sensitive picomole assay of ST6Gal1. Asialoglycopolypeptide was regioselectively and quantitatively sialylated by catalytic reaction at the terminal Gal residue to obtain α2,6-sialoglycopolypeptide using ST6Gal1. The α2,6-sialoglycopolypeptide selectively inhibited hemagglutination induced by Sambucus nigra (SNA) lectin, showing about 780-fold higher affinity than the control fetuin. Asialoglycopolypeptide and γ-polyglutamic acid did not affect SNA lectin-mediated hemagglutination.
Conclusion
The recombinant ST6Gal1 from a silkworm expression system is useful for the sialylation of asialoglycopeptide. The sialylated glycoprotein is a valuable tool for investigating the molecular mechanisms of biological and physiological events, such as cell-cell recognition and viral entry during infection.
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