precursor:
Rhythm and blues was a precursor of rock music.
Small tremors may be precursors to big earthquakes.
The Office of Strategic Services in World War II was the immediate precursor of today's Central Intelligence Agency.
A protein precursor, also called a pro-protein or pro-peptide, is an inactive protein (or peptide) that can be turned into an active form by post-translational modification, such as breaking off a piece of the molecule or adding on another molecule.
