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Crystallographic analysis of oxygenated and deoxygenated states of arthropod hemocyanin shows unusual differences
Author(s) -
Magnus Karen A.,
Hazes Bart,
TonThat Hoa,
Bonaventura Celia,
Bonaventura Joseph,
Hol Wim G. J.
Publication year - 1994
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.340190405
Subject(s) - hemocyanin , limulus , crystallography , arthropod , chemistry , protein subunit , copper , deoxygenated hemoglobin , cooperativity , protein quaternary structure , stereochemistry , biology , biochemistry , hemoglobin , evolutionary biology , ecology , genetics , organic chemistry , antigen , gene
The X‐ray structure of an oxygenated hemocyanin molecule, subunit II of Limulus polyphemus hemocyanin, was determined at 2.4 Å resolution and refined to a crystallographic R ‐factor of 17.1%. The 73‐kDa subunit crystallizes with the symmetry of the space group R 32 with one subunit per asymmetric unit forming hexamers with 32 point group symmetry. Molecular oxygen is bound to a dinuclear copper center in the protein's second domain, symmetrically between and equidistant from the two copper atoms. The copper‐copper distance in oxygenated Limulus hemocyanin is 3.6 ± 0.2 Å, which is surprisingly 1 Å less than that seen previously in deoxygenated Limulus polyphemus subunit II hemocyanin (Hazes et al., Protein Sci. 2:597, 1993). Away from the oxygen binding sites, the tertiary and quaternary structures of oxygenated and deoxygenated Limulus subunit II hemocyanins are quite similar. A major difference in tertiary structures is seen, however, when the Limulus structures are compared with deoxygenated Panulirus interruptus hemocyanin (Volbeda, A., Hol, W. G. J. J. Mol. Biol. 209:249, 1989) where the position of domain 1 is rotated by 8° with respect to domains 2 and 3. We postulate this rotation plays an important role in cooperativity and regulation of oxygen affinity in all arthropod hemocyanins. © 1994 Wiley‐Liss, Inc.