title: Functional and biochemical properties of the hemoglobins of the burrowing brittle star Hemipholis elongata say (Echinodermata, Ophiuroidea).
abstract: The burrowing brittle star Hemipholis elongata (Say) possesses hemoglobin-containing coelomocytes (RBCs) in its water vascular system. The RBCs, which circulate between the arms and body, are thought to play a role in oxygen transport. The hemoglobin of adult animals has a moderate affinity for oxygen (P(50) = 11.4 mm Hg at pH 8, 20 degrees C, measured in cellulo) and exhibits cooperativity (Hill coefficient > 1.7). The hemoglobin of juveniles has a higher affinity (P(50) = 2.3 mmHg at pH 8.0, 20 degrees C) and also exhibits cooperativity. The oxygen-binding properties of the hemoglobin are relatively insensitive to pH, temperature, and hydrogen sulfide. Adult hemoglobin is a heterogeneous mixture composed of three major fractions. The combined results of electrospray mass spectrometry and oxygen-binding experiments performed on purified fractions indicate that the native hemoglobin is in the form of homopolymers. A partial amino acid sequence (about 40 amino acids) of adult hemoglobin reveals little homology with holothurian hemoglobins.
authors.affiliation: Biology Department, Lamar University, PO Box 10037, Beaumont, Texas 77710, USA. christenab@hal.lamar.edu
authors.forename: Ana Beardsley
authors.initials: AB
authors.lastname: Christensen
authors.forename: James M
authors.initials: JM
authors.lastname: Colacino
authors.forename: Celia
authors.initials: C
authors.lastname: Bonaventura
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004447:Echinodermata / Q000502:physiology*; D006454:Hemoglobins / Q000378:metabolism* / Q000502:physiology*; D007700:Kinetics; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism*; D011485:Protein Binding / Q000502:physiology; D013022:South Carolina
chemical_list: D006454:Hemoglobins; D010100:Oxygen