What would be a direct consequence of a single point mutation that modifies the proteins inside the acrosome?

Answer 1

From the Internet:

The function of the acrosome reaction is to help the sperm get through the egg's protective coat and to allow the plasma membranes of the sperm and egg to fuse. ... This has three important consequences: the release of proteolytic enzymes, extension of the acrosomal process, and exposure of membrane proteins.

So, no penetration, no fertilization.