Carson W M, Bowers T R, Kitto G B, Hackert M L
J Biol Chem. 1979 Aug 10;254(15):7400-2.
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.
已制备出海参莫氏海参体腔细胞中两种不同珠蛋白链的大单晶，并通过X射线晶体学进行了检测。这些血红蛋白在生理浓度下呈现出多种配体依赖性缔合状态，其中高铁血红蛋白以单体形式存在，而配体化血红蛋白以二聚体形式存在。单体高铁血红蛋白C链在空间群P21中结晶，a = 46.0 Å，b = 45.3 Å，c = 40.9 Å，β = 104.5°，每个不对称单元有一个单体。用偏光镜检查时，这些晶体表现出异常的光谱行为，在某些取向会变成无色。这意味着晶体中所有的血红素环几乎是平行的。二聚体氰化高铁血红蛋白D链在空间群P41212（P43212）中结晶，a = b = 77.0 Å，c = 61.5 Å，每个不对称单元有二聚体的一半。因此，这些同二聚体具有与晶体学二重轴对齐的分子2重轴。
