Fig. 7.

The general model of KSG action. (A) Binding of KSG to the small ribosomal subunit partially interferes with formation of the 30S IC; (B) KSG blocks either maturation of 70S IC or the first rounds of elongation, thereby arresting the 70S translation complex at the start codon. The nature of the mRNA residue preceding the start codon affects the severity of translation arrest, with G being most conducive to antibiotic action. KSG-arrested ribosomes may dissociate from mRNA or, occasionally, proceed to synthesize the encoded protein. In the latter case, the KSG molecule is likely displaced at the early rounds of translation.