Crystal structure analysis of sea lamprey hemoglobin at 2 Å resolution

Abstract

The crystal structure of the predominant hemoglobin component of blood from the sea lamprey, Petromyzon marinus, has been determined by X-ray diffraction analysis. Crystals for this analysis were grown from cyanide methemoglobin V as crystal type D 2. These crystals are in space group P2 12 12 1 and have unit cell dimensions of a = 44.57 A ̊ , b = 96.62 A ̊ and c = 31.34 A ̊ . Isomorphous heavyatom derivatives were prepared by soaking crystals in solutions of Hg(CN) 2, K 2Hg(CNS) 4 and KAu(CN) 2. Diffracted intensities to as far as 2 Å spacings were measured on a diffractometer. Phases were found by means of the isomorphous replacements and anomalous scattering, with supplementary information provided by the tangent formula. An atomic model was fitted to the final electron density map in a Richards optical comparator. The lamprey hemoglobin molecule is generally similar in structure to other globins, but differs in many details. Each molecule is in contact with ten neighboring molecules in the crystal lattice. The nature of the binding of the heavy atoms to lamprey hemoglobin has been interpreted.