The structure of the giant haemoglobin from Glossoscolex paulistus

• Published in: Acta crystallographica. Section D, Biological crystallography. Vol. 71; no. 6; pp. 1257 - 1271
• Main Authors: Ruggiero Bachega, José Fernando, Vasconcelos Maluf, Fernando, Andi, Babak, D'Muniz Pereira, Humberto, Falsarella Carazzollea, Marcelo, Orville, Allen M., Tabak, Marcel, Brandão-Neto, José, Garratt, Richard Charles, Horjales Reboredo, Eduardo
• Format: Journal Article
• Language: English
• Published: 5 Abbey Square, Chester, Cheshire CH1 2HU, England International Union of Crystallography 01.06.2015; Wiley Subscription Services, Inc
• Subjects: Amino Acid Sequence; Animals; Crystallography, X-Ray; erythrocruorins; giant extracellular haemoglobin; Glossoscolex paulistus; Hemoglobins - chemistry; hexagonal bilayer; Molecular Sequence Data; Oligochaeta - chemistry; Protein Conformation; Sequence Homology, Amino Acid; giant extracellular haemoglobin; hexagonal bilayer; erythrocruorins; Glossoscolex paulistus
• ISSN: 1399-0047; 0907-4449; 1399-0047
• DOI: 10.1107/S1399004715005453

The sequences of all seven polypeptide chains from the giant haemoglobin of the free‐living earthworm Glossoscolex paulistus (HbGp) are reported together with the three‐dimensional structure of the 3.6 MDa complex which they form. The refinement of the full particle, which has been solved at 3.2 Å resolution, the highest resolution reported to date for a hexagonal bilayer haemoglobin composed of 12 protomers, is reported. This has allowed a more detailed description of the contacts between subunits which are essential for particle stability. Interpretation of features in the electron‐density maps suggests the presence of metal‐binding sites (probably Zn2+ and Ca2+) and glycosylation sites, some of which have not been reported previously. The former appear to be important for the integrity of the particle. The crystal structure of the isolated d chain (d‐HbGp) at 2.1 Å resolution shows different interchain contacts between d monomers compared with those observed in the full particle. Instead of forming trimers, as seen in the complex, the isolated d chains associate to form dimers across a crystallographic twofold axis. These observations eliminate the possibility that trimers form spontaneously in solution as intermediates during the formation of the dodecameric globin cap and contribute to understanding of the possible ways in which the particle self‐assembles.