Define role of Vitamin K in controlling gene expression?

Prithrombin, a protein required for blood clotting is assembled with a large number of glutamic acid residues. In the presence of vitamin K, these residues are carboxylated, and this posttranslational change results in a dramatic increase in the calcium binding capacity of the resultant protein. Unless prothrombin can bind calcium, it cannot function in the clotting process. This is another example of how a nutrient can affect gene expression; in this instance, it is the expression of functional prothrombin. The site of the nutritional effect is that or posttranslational protein modification.