Hemoglobins from deep-sea hydrothermal vent scaleworms of the genus Branchipolynoe: A new type of quaternary structure

Branchipolynoe symmytilida and B. seepensis are two scaleworms (Polychaeta; Polynoidae) living commensally in the mantle cavity of deep-sea hydrotherm al vent and cold-seep mussels. In contrast with littoral members of this fa mily, the two species exhibit a large amount of extracellular hemoglobin (H b) in their coelomic fluid. Gel Filtration revealed the existence of four d ifferent Hbs: one minor, high molecular mass (3 10(6) Da) Hb, V1-Hb, remini scent of a vascular hexagonal bilayer annelid Hb; two major coelomic Hbs, C 1-Hb, and C2-Hb, with unusual masses for extracellular annelid Hbs of 153 a nd 124 kDa respectively; and a minor probably coelomic Hb of 23 kDa (C3-Hb) . Using electrospray ionization mass spectrometry, SDS-PAGE after subtilisin treatment, and tandem mass spectrometry, we showed that C1-Hb is a trimer o f a 57,996 Da chain and C2-Hb is a dimer of a 57,648 Da chain, each chain b eing a four-domain/ four-heme polypeptide, This multimeric, multidomain arr angement is unique among annelid Hbs and appears different from that of oth er known multidomain Hbs. Proteins 1999;34:427-434. (C) 1999 Wiley-Liss, In c.