The Pathway for Polypeptides Exported from E

The pathway for polypeptides exported from E. coli includes the following steps, which occur in what order for CORRECT export?
1. A chaperone, SecA, binds to the polypeptide.
2. A chaperone, SecB, binds to the polypeptide.
3. ATP is hydrolyzed by Sec A.
4. SecA pushes 20 amino acids of the polypeptide into the translocation complex.

A) 1, 2, 3, 4
B) 1, 2, 4, 3
C) 2, 1, 4, 3
D) 2, 3, 1, 4
E) 3, 1, 4, 2