Polypeptide chain composition diversity of hexagonal-bilayer haemoglobins within a single family of annelids, the Alvinellidae

Following previous analysis of the structure of Alvinella pompejana heaxago nal-bilayer haemoglobin (HBL Hb) [1], we report in this paper the structure of three other HBL Hbs belonging to Alvinella caudata, Paralvinella grassl ei and Paralvinella palmiformis, members of the Alvinellidae, annelid famil y strictly endemic to deep-sea hydrothermal vents located on the ridge cres ts in the Pacific ocean. The multi-angle laser light scattering (MALLS) and fast protein liquid chromatography (FPLC) analysis revealed a broad range of molecular masses for the extracellular Hb molecules, 3517 +/- 14 kDa (A. caudata), 3822 +/- 28 kDa (P. grasslei) and 3750 +/- 150 kDa (P. palmiform is). Native and derivative Hbs (reduced, carbamidomethylated and deglycosyl ated) were analysed by electrospray ionization mass spectroscopy (ESI-MS) a cid the data was processed by the maximum entropy deconvolution system (Max Ent). The most important difference between alvinellid HBL Hbs was the vari ation in their composition, from two to four monomeric globin chains, and f rom one to four linker chains. Therefore, despite the fact that all these s pecies belong to a single family, notable differences in the polypeptide ch ain composition of their HBL Hbs were observed, probably accounting for the ir different functional properties as previously reported by this group.