Not True Statement about Hemerythrin
Some key points about hemerythrin need to be considered to identify the statement which is not true.

Hemerythrin Overview
- Hemerythrin is a metalloprotein that contains iron and is involved in oxygen transport and storage in certain marine invertebrates.
- It has a unique structure with two iron atoms bound to the protein, which gives it a characteristic pink color when oxygenated.

Key Points
- Hemerythrin does not contain copper as a metal cofactor. Instead, it utilizes iron to bind and transport oxygen.
- Hemerythrin is not found in mammals, but rather in marine invertebrates such as sipunculid worms and brachiopods.
- Hemerythrin does not bind oxygen using a heme group like hemoglobin or myoglobin; instead, it uses the iron atoms within the protein structure.

Explanation
The statement that hemerythrin contains copper as a metal cofactor is not true. Hemerythrin utilizes iron, not copper, to bind and transport oxygen. The presence of iron in hemerythrin is essential for its oxygen-binding capabilities. Therefore, any statement indicating the presence of copper in hemerythrin would be inaccurate.