You are not currently logged in.
Access JSTOR through your library or other institution:
If You Use a Screen ReaderThis content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Copper-Metallothioneins in the American Lobster, Homarus americanus: Potential Role as Cu(I) Donors to Apohemocyanin
Marius Brouwer, Patrick Whaling and David W. Engel
Environmental Health Perspectives
Vol. 65 (Mar., 1986), pp. 93-100
Published by: The National Institute of Environmental Health Sciences
Stable URL: http://www.jstor.org/stable/3430168
Page Count: 8
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Preview not available
The physiological function of copper(I)-metallothionein is not well understood. The respiratory function of hemocyanin, a copper(I)-containing respiratory protein found in the hemolymph of many invertebrates, has been known a long time. However, the mechanism by which Cu(I) is inserted into the oxygen-binding site of apohemocyanin is completely unknown. This investigation tests the hypothesis that copper(I)-metallothionein may act as a Cu(I) donor to apohemocyanin. To this end, copper-binding proteins and hemocyanin were purified from the digestive gland and hemolymph of the American lobster, Homarus americanus. In the presence of β-mercaptoethanol, the copper-binding proteins can be resolved into three components on DEAE-cellulose. The first two have been characterized as metallothioneins, based on their high cysteine content and lack of aromatic amino acid residues. The cysteine content of the third component is half of that of components I and II. In the absence of β-mercaptoethanol the three proteins elute as a single protein complex during ion-exchange chromatography. Components I and II show a strong tendency to polymerize, a process that is accompanied by the loss of protein-bound copper. The purified proteins are not capable of transferring Cu(I) to the active sites of completely copper-free apohemocyanin. They are capable, however, of transferring Cu(I) to active sites of hemocyanin containing reduced amounts of Cu(I), suggesting that the conformational state of hemocyanin is the determining factor in the Cu(I) transfer mechanism.
Environmental Health Perspectives © 1986 The National Institute of Environmental Health Sciences