QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Hourdez, S. Articles by Fisher, C. R. Search for Related Content PubMed PubMed Citation Articles by Hourdez, S. Articles by Fisher, C. R.

Respiratory adaptations in a deep-sea orbiniid polychaete from Gulf of Mexico brine pool NR-1: metabolic rates and hemoglobin structure/function relationships

Stéphane Hourdez^1,2,*, Roy E. Weber³, Brian N. Green⁴, John M. Kenney⁵ and Charles R. Fisher¹

¹ Department of Biology, 208 Mueller Lab, Pennsylvania State University, University Park, PA 16802, USA
² Station Biologique de Roscoff, BP74, CNRS-UPMC-INSU, 29682 Roscoff cedex, France
³ Center for Respiratory Adaptation (CRA), Department of Zoophysiology, University of Aarhus, 8000 Aarhus C, Denmark
⁴ Micromass Ltd, Tudor Road, Altrincham, Cheshire WA14 5RZ, UK
⁵ Institute for Storage Ring Facilities — Aarhus (ISA), University of Aarhus, 8000 Aarhus C, Denmark
^* Present address: Department of Biology, 208 Mueller Lab, Pennsylvania State University, University Park, PA 16802, USA

View larger version (19K): [in a new window]   Fig. 1. Experimental apparatus used for respiration measurements at controlled temperature.

View larger version (24K): [in a new window]   Fig. 2. Oxygen consumption for a specimen (1.24 g wet mass) of Methanoaricia dendrobranchiata at 8 °C. (A) Changes in the oxygen concentration in the chamber during the experiment. Readings were taken every 5 min. (B) Calculated oxygen consumption rate as a function of oxygen concentration for the same worm. Regression (i): r2=0.006, N=54, P=0.589; regression (ii): r2=0.903, N=20, P<0.0005. Pc, critical pressure.

View larger version (11K): [in a new window]   Fig. 3. Relationship between oxygen consumption rate and wet mass of Methanoaricia dendrobranchiata. The line fits the equation: O2=0.488M-0.702, r2=0.457, P<0.1.

View larger version (20K): [in a new window]   Fig. 4. Percentage survival of Methanoaricia dendrobranchiata under normoxia, anoxia, anoxia + 60 µmol l-1 sulfide and anoxia +1 mmol l-1 sulfide. Twenty-two worms were exposed to each condition.

View larger version (13K): [in a new window]   Fig. 5. Hemoglobin content as a function of wet mass for Methanoaricia dendrobranchiata (N=61). The dotted line fits the equation: Q=0.256M0.056, P<0.01.

View larger version (147K): [in a new window]   Fig. 6. Evidence for the hexagonal bilayer (HBL) structure of Methanoaricia dendrobranchiata hemoglobin. (A) Negatively stained electron microscope image of M. dendrobranchiata hemoglobin. The dark areas are stain. The protein of the molecular complex appears pale. The hemoglobin molecular complexes are in various orientations. The top and side views (indicated) appear to be similar to the top (sixfold) and side (twofold) views of other annelid hemoglobins. Scale bar, 200 nm. (B) An image of a typical top view taken from the electron microscope image in A. Scale bar, 30 nm. (C) Rotational frequency analysis of image B showing the strong sixfold symmetry expected of an HBL. (D) The sixfold rotationally Fourier-filtered image of B. The sub-structure, such as the density in the middle and the holes within the six subunits, is similar to that of other HBLs. Scale bar, 30 nm.

View larger version (21K): [in a new window]   Fig. 7. Example mass spectra (one of five) of the 3.5x106 Da hemoglobin under (A) non-reducing, (B) reducing and (C) reduced and carboxyamidomethylated (Cam) conditions. (D) Model of structure of the globin monomers and dimers. The inset in A shows the linker dimers on the same intensity scale as in A but on an expanded mass scale. a1-a4, b and c, globin chain subunits; LD1-LD4, linker dimers; Dm, globin dimer; x2, portion of the spectrum where intensity has been multiplied by 2.

View larger version (25K): [in a new window]   Fig. 8. Effect of pH on the affinity (P50 in mmHg; 1 mmHg=0.133 kPa) and cooperativity (n50) of the intact hemoglobin (W-Hb) and putative dodecameric fraction (D) at 10, 20 and 30°C. Numbers in italics show the Bohr factors () for the pH range 6.8-7.5. Buffer, 0.125 mol l-1 Hepes in Riftia saline. Heme concentration, 0.51 mmol l-1 (W-Hb) and 0.22 mmol l-1 (D).

View larger version (26K): [in a new window]   Fig. 9. Extended Hill plot of the intact hemoglobin at 20°C pH 6.77 and 7.60. As indicated, the intersections between the lower and upper asymptotes to the Hill plot with the y-axis at logPo2-0, indicate the values of logKT and logKR, respectively. Other conditions as in Fig. 8. KR, oxygen-binding affinity of the hemoglobin in the oxygenated (relaxed) state; KT, oxygen-binding affinity of the hemoglobin in the deoxygenated (tense) state; Y, saturation.

View larger version (21K): [in a new window]   Fig. 10. Arrhenius plot for both the intact hemoglobin (W-Hb; open symbols) and the dodecameric fraction (Dodec; filled symbols) at pH 6.8 and 7.6. Other conditions as in Fig. 8. P50, oxygen partial pressure at half-saturation; T, absolute temperature. 1 mmHg=0.133 kPa.

View larger version (22K): [in a new window]   Fig. 11 . Example of the effect of [Ca2+] on the oxygen affinity (P50 in mmHg) and cooperativity (n50) of the intact hemoglobin and its dodecamers at pH 7.0. Heme concentration, 0.32 mmol l-1. W-Hb, intact hemoglobin; D, dodecameric fraction. 1 mmHg=0.133 kPa. Open columns, [Ca2+]=0 mmol l-1; stippled columns, [Ca2+]=0.1 mmol l-1.

View larger version (18K): [in a new window]   Fig. 12. Sulfide- and anoxia-tolerance in some polychaete species. Data from Schiedeck et al. (1997), Gamenick et al. (1998) and Groenendaal (1980) are also plotted. TL50, 50 % survival rate. S. L and I are isolates in the Capitella species complex.