title: Preliminary crystallographic data on monomeric and dimeric hemoglobins from the sea cucumber, Molpadia arenicola.
abstract: Large single crystals of two distinct globin chains from coelomic cells of the sea cucumber Molpadia arenicola have been prepared and examined by x-ray crystallography. These hemoglobins exhibit a variety of ligand-dependent association states with the met-hemoglobins existing as monomers and liganded hemoglobins as dimers at physiological concentrations. Monomeric methemoglobin C chain crystallizes in space group P21, with a = 46.0 A, b = 45.3 A, c = 40.9 A, beta = 104.5 degrees, and one monomer per asymmetric unit. These crystals exhibit unusual spectroscopic behavior when examined with a polarizer, turning colorless in certain orientations. This implies that all the heme rings are nearly parallel within the crystals. Dimeric cyanmethemoglobin D chain crystallizes in space group P41212 (P43212), with a = b = 77.0 A, c = 61.5 A, and one-half a dimer per asymmetric unit. These homodimers thus possess a molecular 2-fold which is aligned with the crystallographic dyad.
mesh_terms: D000818:Animals; D004447:Echinodermata / Q000032:analysis*; D006454:Hemoglobins; D046911:Macromolecular Substances; D011487:Protein Conformation; D012616:Sea Cucumbers / Q000032:analysis*; D014961:X-Ray Diffraction
chemical_list: D006454:Hemoglobins; D046911:Macromolecular Substances