Final answer:
The statement in question is false, as IF-3 binds to the 30S ribosomal subunit to prevent the early combination with the 50S subunit and is released after the 50S subunit binds to form the 70S initiation complex.
Step-by-step explanation:
The statement 'IF-3 must be released before the 50S subunit binds' is false. The protein synthesis process begins with the initiation stage where initiation factor 3 (IF3) binds to the 30S ribosomal subunit to prevent its premature association with the 50S subunit. IF3 remains attached to the 30S subunit until an initiator tRNA and mRNA are properly positioned.
During the final steps of initiation, the large 50S ribosomal subunit will join the complex, forming a functional 70S initiation complex ready for the elongation stage of protein synthesis. At this time, after the 50S subunit joins, IF3 is released along with other initiation factors, such as IF1 and IF2, facilitated by the hydrolysis of GTP to GDP and Pi.
This assembly process ensures that the mRNA and tRNA are in place before the ribosome becomes fully functional with both its subunits. Therefore, IF-3 disassociation occurs after the 50S subunit has successfully bound to form the complete ribosome, not before.