Limulus polyphemus Hemocyanin: 10 Å Cryo-EM Structure, Sequence Analysis, Molecular Modelling and Rigid-body Fitting Reveal the Interfaces Between the Eight Hexamers

Abstract The blue copper protein hemocyanin from the horseshoe crab Limulus polyphemus is among the largest respiratory proteins found in nature (3.5 MDa) and exhibits a highly cooperative oxygen binding. Its 48 subunits are arranged as eight hexamers (1×6mers) that form the native 8×6mer in a nested hierarchy of 2×6mers and 4×6mers. This quaternary structure is established by eight subunit types (termed I, IIA, II, IIIA, IIIB, IV, V, and VI), of which only type II has been sequenced. Crystal structures of the 1×6mer are available, but for the 8×6mer only a 40 A 3D reconstruction exists. Consequently, the structural parameters of the 8×6mer are not firmly established, and the molecular inte…

3-D reconstruction of hemocyanins and other invertebrate hemolymph proteins by cryo-TEM: an overview.

Quaternary structure of the European spiny lobster (Palinurus elephas) 1x6-mer hemocyanin from cryoEM and amino acid sequence data.

Abstract Arthropod hemocyanins are large respiratory proteins that are composed of up to 48 subunits (8×6-mer) in the 75 kDa range. A 3D reconstruction of the 1×6-mer hemocyanin from the European spiny lobster Palinurus elephas has been performed from 9970 single particles using cryoelectron microscopy. An 8 A resolution of the hemocyanin 3D reconstruction has been obtained from about 600 final class averages. Visualisation of structural elements such as α-helices has been achieved. An amino acid sequence alignment shows the high sequence identity (>80%) of the hemocyanin subunits from the European spiny lobster P. elephas and the American spiny lobster Panulirus interruptus . Comparison of…

Quaternary structure and molecular model of a 4x6mer arthropod hemocyanin in oxygenated and deoxygenated states by 3D cryo-electron microscopy

Extended abstract of a paper presented at MC 2007, 33rd DGE Conference in Saarbrücken, Germany, September 2 – September 7, 2007