Structural and functional properties of hemoglobin from the vestimentiferan Pogonophora, Lamellibrachia
Representatives of the phylum Pogonophora were found at 1800 m in a fault region off San Diego, CA, where there were indications of recently discharged hydrothermal fluids. The worm-like organisms were determined to be Lamellibrachia sp, phylogenetically related to Riftia pachyptila, a Pogonophora from the Galapagos Rift hydrothermal vent site whose hemoglobins were previously studied. Lamellibrachia extracellular hemoglobin was found to be heterogeneous with respect to its state of aggregation. Two tiered hexagonal structures, as described for annelid hemoglobin, with molecular weights of approx. 3 · 106, make up 25-40% of the hemoglobin, while the other hemoglobin fraction has a molecular weight of 300 000-400 000. The two molecular weight fractions have different subunit compositions and are not in equilibrium with one another. Their amino acid compositions differ slightly. Both fractions contain 1 mol of heme per approx. 25 000 g of protein. The unfractionated hemoglobin has a high oxygen affinity (P50 = 0.16 Torr, 20°C) and little or no pH sensitivity, and shows cooperative subunit interactions (nH = 2-2.7). Lamellibrachia hemoglobin closely resembles the extracellular hemoglobins of annelids in many respects but shares the molecular weight heterogeneity previously reported for hemoglobin of R. pachyptila. © 1985.
Terwilliger, R; Terwilliger, N; Bonaventura, C; Bonaventura, J; Schabtach, E
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