– One of the primary rRNA binding proteins, it binds directly to 16S rRNA where it nucleates assembly of the head domain of the 30S subunit. Is located at the subunit interface close to the decoding center, where it has been shown to contact mRNA. Has been shown to contact tRNA in both the P and E sites; it probably blocks exit of the E site tRNA.; Protein S7 is also a translational repressor protein; it regulates the expression of the str operon members to different degrees by binding to its mRNA.