3J32

An asymmetric unit map from electron cryo-microscopy of Haliotis diversicolor molluscan hemocyanin isoform 1 (HdH1)

Summary for 3J32

• Entry DOI: 10.2210/pdb3j32/pdb
• EMDB information: 5585 5586
• Descriptor: Hemocyanin isoform 1 (1 entity in total)
• Functional Keywords: allosteric, oxygen transport
• Biological source: Haliotis diversicolor (Abalone)
• Total number of polymer chains: 2
• Total formula weight: 757345.62

Authors

Zhang, Q.,Dai, X.,Cong, Y.,Zhang, J.,Chen, D.-H.,Dougherty, M.,Wang, J.,Ludtke, S.,Schmid, M.F.,Chiu, W. (deposition date: 2013-02-20, release date: 2013-04-17, Last modification date: 2024-02-21)

Primary citation

Zhang, Q.,Dai, X.,Cong, Y.,Zhang, J.,Chen, D.H.,Dougherty, M.T.,Wang, J.,Ludtke, S.J.,Schmid, M.F.,Chiu, W.
Cryo-EM structure of a molluscan hemocyanin suggests its allosteric mechanism.
Structure, 21:604-613, 2013

PubMed Abstract: Hemocyanins are responsible for transporting O2 in the arthropod and molluscan hemolymph. Haliotis diversicolor molluscan hemocyanin isoform 1 (HdH1) is an 8 MDa oligomer. Each subunit is made up of eight functional units (FUs). Each FU contains two Cu ions, which can reversibly bind an oxygen molecule. Here, we report a 4.5 A° cryo-EM structure of HdH1. The structure clearly shows ten asymmetric units arranged with D5 symmetry. Each asymmetric unit contains two structurally distinct but chemically identical subunits. The map is sufficiently resolved to trace the entire subunit Ca backbone and to visualize densities corresponding to some large side chains, Cu ion pairs, and interaction networks of adjacent subunits. A FU topology path intertwining between the two subunits of the asymmetric unit is unambiguously determined. Our observations suggest a structural mechanism for the stability of the entire hemocyanin didecamer and 20 ‘‘communication clusters’’ across asymmetric units responsible for its allosteric property upon oxygen binding.

PubMed: 23541894
DOI: 10.1016/j.str.2013.02.018

Experimental method

ELECTRON MICROSCOPY (4.5 Å)