Hexamers of subunit II from Limulus hemocyanin (a 48-mer) have the same quaternary structure as whole Panulirus hemocyanin molecules.
Hemocyanins are copper-containing proteins that transport oxygen in a variety of invertebrates. Considerable evidence has accumulated that arthropodan hemocyanins are multimers of a fundamental hexameric unit. X-Ray crystallographic structure determination has revealed that the hemocyanin molecule from the spiny lobster Panulirus interruptus is a single hexamer having 32 point group symmetry. Using crystals of subunit II, one of 8 polypeptide types comprising the octahexameric hemocyanin of the horseshoe crab Limulus polyphemus, and the molecular replacement method for crystallographic phase determination we show that subunit II forms assemblies with the same hexameric quaternary structure as the whole Panulirus hemocyanin molecule. Observation of the same hexameric motif in two widely separated species provides strong additional evidence that this quaternary structural unit is a universal building block of arthropodan hemocyanins.
Magnus
K A
KA
Department of Biophysics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
Lattman
E E
EE
Volbeda
A
A
Hol
W G
WG
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D006433:Hemocyanins / Q000737:chemistry* / Q000378:metabolism; D006737:Horseshoe Crabs; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008121:Nephropidae; D010100:Oxygen / Q000378:metabolism; D011487:Protein Conformation; D013237:Stereoisomerism; D014961:X-Ray Diffraction
D006433:Hemocyanins; D010100:Oxygen