Three-Dimensional Structure of Haemocyanin from the Spiny Lobster, Panulirus Interruptus, at 3.2 Å Resolution

Abstract

Haemocyanins are the non-haem, copper-containing oxygen transporting molecules occurring freely dissolved in the haemolymph of a large number of invertebrate species. The molecular architectures of the two known classes of haemocyanins are entirely different. Molluscan haemocyanins have the form of cylinders, with 10–20 subunits forming the complete molecules with molecular weights up to about ten million daltons. The subunits are made up by maximally 8 “repeated” domains, each of which has one dinuclear copper site. Arthropodan haemocyanins are composed of hexamers, or multi-hexamers, with individual subunits having molecular weights in the order of 75.000 daltons, each subunit containing one pair of copper ions. Complete molecules range from single hexamers of ~ 460.000 daltons to octa-hexamers with molecular weights of something like 3.7 million. All haemocyanins are thus large molecules, but some are larger than others (1–3).