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Establishment of two distinct protein domains in blue crab Callinectes sapidus metallothionein‐I through heteronuclear ( 1 H 113 Cd) and homonuclear 1 H 1 H) correlation NMR experiments
Author(s) -
Narula Surinder S.,
Armitage Ian M.,
Brouwer Marius,
Enghild Jan J.
Publication year - 1993
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260311319
Subject(s) - chemistry , metallothionein , callinectes , heteronuclear molecule , homonuclear molecule , cysteine , metal , cadmium , divalent , metal ions in aqueous solution , zinc , stereochemistry , crystallography , nuclear magnetic resonance spectroscopy , biochemistry , molecule , crustacean , organic chemistry , ecology , biology , enzyme
Metallothionein is a cysteine‐rich metal‐binding protein whose biosynthesis is closely regulated by the level of exposure of an organism to zinc, copper, cadmium, etc., metal salts. The metallothionein from the crab Callinectes sapidus is known to bind six divalent metal ions. The 113 Cd NMR spectrum of the 113 Cdsubstituted protein shows six distinct 113 Cd resonances spanning a chemical shift range of 620–665 ppm, indicating the presence of six distinct tetrahedrally coordinated divalent metal ion binding sites. Heteronuclear 1 H 113 Cd correlation experiments revealed all the metal‐to‐cysteine connectivities present in this protein and the 2X(2 113 Cd)‐;filtered COSY experiment revealed that six cysteines are involved in the ligation of two Cd 2+ ions. Additionally, following the complete sequential resonance assignment of the 1 H NMR data, the two separate Cd 3 Cys 9 metal binding clusters can be shown to reside in two distinct protein domains.