Supramolecular protein–protein complexation via specific interaction between glycosylated myoglobin and sugar-binding protein

Abstract

Two different types of artificial glycosylated haemins (glycohaemins), in which a monosaccharide (galactose) or a disaccharide (lactobionic acid, 4-O-β-galactopyranosyl-d-gluconic acid) was introduced at the terminals of the two haem-propionate side chains, were synthesised to serve as a designed interface on the myoglobin surface. These glycohaemins were successfully inserted into apomyoglobin to yield an artificial glycoprotein by the conventional method. The interprotein interaction between the reconstituted myoglobin and peanut agglutinin lectin (PNA), a β-galactose-recognising protein, was confirmed by two different assay systems, i.e. a fluorometric assay using the fluorescein isothiocyanate-labelled lectin and an ELISA-like assay using the peroxidase-labelled lectin. The results revealed that each myoglobin reconstituted with the glycohaemin makes a complex with PNA, in which the glycoprotein with the disaccharides showed a higher binding affinity with the lectin compared to the glycoprotein with the monosaccharides, suggesting that the binding property clearly depends on the deposited carbohydrate surface on the myoglobin.

Keywords:

• protein–protein complex
• haemoprotein modification
• haem-substitution
• artificial glycoprotein

Acknowledgements

We are grateful to Prof. Hiroshi Uyama (Osaka University) and Dr Eiko Mochizuki (Osaka University) for their kind help in the enzyme assays. This work was supported by MEXT and JSPS. One of the authors, H.N., expresses his special thanks to the Global COE (Center of Excellence) Program ‘Global Education and Research Center for Bio-Environmental Chemistry’ of Osaka University.

Notes

^1. The apoprotein was formed under ionisation condition.