Wheat germ agglutinin-reactive chains of giant hemoglobin from the polychaete Perinereis aibuhitensis

Abstract

Wheat germ agglutinin-reactive chains of multisubunit extracellular hemoglobin from the polychaete Perinereis aibuhitensis were identified to clarify the carbohydrate gluing which is the carbohydrate-dependent supramolecular architecture of the hemoglobin (Ebina S. et al. (1995) Proc. Natl. Acad. Sci. USA 92, 7367–7371). Electron microscope micrographs of Perinereis hemoglobin showed a characteristic shape of two-tiered hexagonal rings whose diameter and height were determined to be 29.4 ± 1.7 nm and 20.0 ± 1.8 nm, respectively. Four types of globins and two types of linkers were isolated from the giant hemoglobin by reverse-phase chromatography and SDS-PAGE. These constituents showed similar NH 2-terminal sequences as those previously reported for corresponding chains of Tylorrhynchus hemoglobin (Suzuki T. and Gotoh T. (1986) J. Biol. Chem. 261, 9257–9267; Suzuki T. et al. (1990) J. Biol. Chem. 265, 12168–12177). Thus, each globin of Perinereis hemoglobin was identified in terms of amino acid sequence homology and designated using names common to Tylorrhynchus hemoglobin, namely, a, A, b, and B. The linkers were stained by horseradish peroxidase (HRP)-lectins and PAS staining kits, indicating the presence of carbohydrate oligomers. Lectin staining was also significantly positive to globins a and A, which belong to strain A, but negative to globins b and B, which belong to strain B. Results showed that linkers and globins of strain A had a site in a carbohydrate oligomer to which wheat germ agglutinin (WGA) could bind. On the other hand, an alignment between known amino acid sequences of annelid globins and linkers and the sequences of lectins revealed that only the domain of the cysteine-rich motif in linkers has a homology with WGA-type lectins. The results of this study clarify the structuring mechanism of a supramolecule by lectin-like binding, called carbohydrate gluing.