Tomcod from the Hudson River have a variant protein that makes them less sensitive to the toxic effects of PCBs.  The effects of PCBs occur through their interaction with a protein called Aryl Hydrocarbon Receptor 2 (AHR2).  AHR2 is normally inactive, but when PCB molecules bind to it, AHR2 becomes activated and acts as a molecular switch to turn on other genes that lead to toxicity (“Effects” in the figure).  Tomcod such as those from Shinnecock Bay, Long Island, NY (left panel) have a normal version of the AHR2 protein, which has a high affinity for PCBs. Tomcod from the Hudson River (right panel) have a variant AHR2 protein that is missing two amino acids (building blocks of proteins). Without these two amino acids, the AHR2 from Hudson River fish has a reduced ability to bind PCBs as compared to the normal AHR2 protein. This makes the Hudson River fish less sensitive to the effects of PCBs.  Killifish from New Bedford Harbor also variants of AHR2, but the functional differences have not yet been identified.  For additional details, see Mechanisms and Impacts of Dioxin Resistance in Fish. (figure drawn by Jack Cook (WHOI))



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Last updated December 12, 2016
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