6533b825fe1ef96bd12829ea

RESEARCH PRODUCT

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

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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 the P. elephas hemocyanin electron microscopy (EM) density map with the known P. interruptus X-ray structure shows a close structural correlation, demonstrating the reliability of both methods for reconstructing proteins. By molecular modelling, we have found the putative locations for the amino acid sequence (597–605) and the C-terminal end (654–657), which are absent in the available P. interruptus X-ray data.