INVESTIGATION BY ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY OF THE EXTRACELLULAR HEMOGLOBIN FROM THE POLYCHAETE ANNELID ALVINELLA-POMPEJANA - AN UNUSUAL HEXAGONAL BILAYER HEMOGLOBIN

Alvinella pompejana inhabits deep-sea, hydrothermal vent sites along t he East-Pacific Rise, where it colonizes the walls of actively venting high-temperature chimneys. This worm is the most thermophilic metazoa n known to date. In Alvinella, as in other alvinellids, oxygen transpo rt is mainly achieved by an extracellular Hb dissolved in the vascular blood. This Hb has a molecular mass of 3833 +/- 14 kDa as revealed by multiangle laser light scattering (MALLS). Native and derivative Hb ( reduced, carbamidomethylated, and deglycosylated) were analyzed by ele ctrospray ionization mass spectrometry (ESI-MS). The data were process ed by the maximum entropy deconvolution system (MaxEnt). We identified three groups of peaks for Alvinella Hb, at cn. 16, 23-26, and 50 kDa corresponding to (i) four monomeric globin chains, al (16 633.4), a2 ( 16 532.4), a3 (16 419.6), and a4 (16 348.9); (ii) four linker chains, L1-L4 (22 887.1, 24 230.5, 26 233.6, and 25 974.4); and (iii) one disu lfide-bonded trimer T (51 431.9) composed of globin chains b (16 477.5 ), c (16 916.1), and d(18 048.8). These Hbs were also subjected to SDS -PAGE analysis for comparative purposes. In addition, using the ESI-MS data we propose two alternative models for the quaternary structure o f Alvinella's Hb.