CRYSTALLOGRAPHIC INVESTIGATIONS OF ERYTRHROCRUORIN FROM LUMBRICUS TERRESTRIS. by Kristen Strand and William Royer, Jr., Program in Molecular Medicine and Dept. of Biochemistry and Molecular Biology, University of Massachusetts Medical Center, Worcester MA 01605.

Lumbricus hemolglobin is an extracellular respiratory protein complex located in the hemolymph of the common earthworm where it functions to transport oxygen and carbon dioxide. It is composed of four unique heme binding polypeptides (abcd chains) and three linker chains which are required for assembly of the entire molecule. We are investigating the crystal structure of the entire molecule and isolated subunits in order to learn the mechanism for the self-limited assembly of a cooperative complex from more than 200 polypeptide chains. We have recently crystallized the abcd assemblage in 2.2 M phosphate buffer pH 6.7. These crystals show symmetry of the space group C2221 and diffraction corresponding to at least 2.8 Å resolution with cell constants of a=138.2 b=171.1 and c=201.2 Å. We have also grown crystals in which the Calcium has been replaced with various Lanthanides. The modulationof diffraction intensities at different wavelengths due to anomalous scattering of these lanthanides will be used tosolve the phases problem. The structure of the abcd complex will then be fitted into cryo-electron microscopy imagesof Lumbricus erythrocruorin in order to provide initialphases for the whole molecule crystal diffraction data.