Assembly map for the 30S subunit

a. Assembly pathway in vitro, as determined by Traub and Nomura.

Arrows indicate the obligatory nature of some protein-binding events.

For example, S7 must bind before S9, S13, or S19, but once S7 is bound, any of these three proteins can be added.

The earliest protein-binding events occur near the 5’ end of the 16S rRNA, and an intermediate to which 5’ - and central-domain proteins are bound must be formed before addition of 3’ domain proteins.

b. In vivo assembly map, as determined by Williamson and colleagues.

Parallel pathways begin, with proteins added at either the 5’ domain or the 3’ domain of 16S rRNA.