The dominant substrate of protein kinase C in the extracts of pig granulocytes is a 38 kDa Ca2+/membrane binding protein.

In the crude extracts of pig granulocytes the dominant substrate of endogenous protein kinase C was a 38 kDa protein. This protein was found in the cytosolic extract when the cells were sonicated in the presence of EGTA but it was bound to the membrane fraction when the cells were sonicated in the presence of Ca2+. The phosphorylation of the 38 kDa protein was absolutely Ca2+/phospholipid dependent. The behaviour of this protein kinase C substrate indicated that it was a lipocortin.