9 Å cryo-EM structure and molecular model of a gastropod hemocyanin didecamer (KLH1) reveals the architecture of the asymmetric collar

Abstract

Hemocyanins are blue copper proteins that transport oxygen in the hemolymph of many arthropods and molluscs. Molluscan hemocyanins are decamers, didecamers or multidecamers of a 350–400 kDa polypeptide subunit that is subdivided into seven or eight different functional units (FUs, each with a single copper active site). The quaternary structure is a semi-hollow cylinder consisting of a wall and a collar. Recently, we published a 9 Å cryo-EM structure and molecular model of a cephalopod hemocyanin decamer (NpH, from Nautilus pompilius) that answered many hitherto unsolved questions concerning the quaternary structure of molluscan hemocyanin. Notably, it revealed the twisted pathway of the 10 subunit copies (each with seven FUs) and the various molecular interfaces between the 70 FUs [1]. Six FU types (termed NpH-a through NpH-f) constitute the cylinder wall, whereas the seventh type (NpH-g) forms the internal collar.