How do you determine molar m based on osmotic pressure?

You are working as an intern in a biochemistry lab. Your advisor just isolated an enzyme and asks you to determine its molar m using osmosis. You dissolve 1.0 g of the enzyme in water to make 250 ml of solution. You measure the osmotic pressure, and find it to be 3.5 torr at 298 K. What is the molar m?