Structure, Function and Transcriptional Regulation of a Copper-Specific Metallothionein in Callinectes sapidus

University Of Southern Mississippi, Hattiesburg MS

Investigators

Abstract

ABSTRACT Proposal MCB-0080075 PI: Marius Brouwer Organisms are dependent on trace metals such as iron and copper for various functions. However, when these metals are in excess they may have toxic effects. The goal of this research project is to further our understanding of the molecular strategies used by organisms to convert potentially toxic copper into a biologically useful form, while avoiding its toxic side effects. Many organisms use metal-specific proteins, called metallothioneins, for detoxification of toxic metals, such as cadmium and mercury, and for detoxification of excess essential metals, such as copper. This project uses the blue crab, an organism that has a very active copper metabolism associated with the synthesis and degradation of hemocyanin, a copper-dependent protein used by the animal to carry oxygen from the gills to the tissues. Earlier work has found that crabs have metallothioneins that are controlled by zinc, as in vertebrates, but also have a copper-specific metallothionein whose synthesis is controlled by copper and not by zinc. This research project has three objectives. First, the hypothesis that the copper-specific metallothionein can provide copper that is required for the biosynthesis of hemocyanin will be examined. These studies may reveal a novel biological function for this new member of the metallothionein family. Secondly, since understanding of the function of a protein at the molecular level requires knowledge of its structure, the three-dimensional structure of the metallothionein protein will be determined. These studies will provide the first structure of a copper-metallothionein of a higher organism. Thirdly, the transcriptional control of the copper-metallothionein gene will be studied. This work may result in the first demonstration of a copper-sensing transcription factor in a higher organism, and may provide the foundation upon which further studies on copper sensing and signaling in higher organisms may be based.