Which metal ion must DNA polymerase bind in order to function?

1. Cofactors are inorganic ions required for optimal regulation of enzyme activity. 2. DNA polymerase, the enzyme that builds DNA molecules, is given as an example of an enzyme needing a metal ion cofactor. 3. It requires a bound zinc ion to function. 4. Iron and magnesium are named as examples of cofactors in general, but zinc is the one attached to DNA polymerase. 5. Calcium and sodium are transported by membrane pumps in cells but are not named as this enzyme's cofactor. 6. Binding the right cofactor promotes optimal conformation and function for the enzyme. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 6 "Metabolism", section 6.5 Enzymes_