Characterization studies on the cadmium-binding proteins from two species of New Zealand oysters.
Two different types of New Zealand oysters--Ostrea lutaria (OL) and Crassostrea glomerata (CG)--contained different concentrations of zinc, copper, and cadmium. OL oysters had 5.3 micrograms Cd/g, 3.4 micrograms Cu/g, 100 micrograms Zn/g; CG oysters had 1.4 micrograms Cd/g and 936 micrograms Zn/g. Both kinds of oysters were shown by gel filtration (G-75) to contain cadmium and zinc in fractions corresponding to a high molecular weight protein (corresponding to the size of albumin or larger) which was heat labile. OL oysters contained cadmium in fractions corresponding to a molecular weight of approximately 6500. The cadmium-binding protein in these fractions was heat-stable. This protein contained no detectable amounts of zinc and was not present in the CG oysters. Further purification by gel filtration (G-50) was performed to obtain a purer protein fraction. Isoelectric focusing of the protein obtained by G-50 filtration showed one main fraction of protein with a pI approximately 5.9 at approximately 13 degrees C. CG oysters contained cadmium and zinc in a polypeptide with low molecular weight (MW 1000). The cadmium-binding oyster proteins are minimally reactive in a competitive binding radioimmunoassay in comparison to the reactivity of a typical vertebrate metallothionein; the proteins may be metallothioneins, but, if so, they do not exhibit the principal determinants characteristic of vertebrate metallothioneins.
Nordberg
M
M
Nuottaniemi
I
I
Cherian
M G
MG
Nordberg
G F
GF
Kjellström
T
T
Garvey
J S
JS
D000818:Animals; D002104:Cadmium / Q000378:metabolism; D002850:Chromatography, Gel; D003300:Copper / Q000378:metabolism; D007526:Isoelectric Point; D008668:Metallothionein / Q000032:analysis / Q000378:metabolism*; D010125:Ostreidae / Q000032:analysis / Q000378:metabolism*; D013045:Species Specificity; D015032:Zinc / Q000378:metabolism
C004203:cadmium-binding protein; D002104:Cadmium; D003300:Copper; D008668:Metallothionein; D015032:Zinc