Kasugamycin (KSG)

Kasugamycin is exists as a white, crystalline substance with the chemical formula C₁₄H₂₈ClN₃O₁₀ . The X-ray structure of kasugamycin in complex with the Escherichia coli 70S ribosome has been determined at 3.5-A resolution. The structure reveals that the drug binds within the messenger RNA channel of the 30S subunit between the universally conserved G926 and A794 nucleotides in 16S ribosomal RNA, which are sites of kasugamycin resistance. The kasugamycin binding sites are present on top of helix 44 (h44), spanning the region between h24 and h28, which contacts the conserved nucleotides A794 and G926. Neither binding position overlaps with P-site tRNA. Instead, kasugamycin mimics the codon nucleotides at the P and E sites by binding within the path of the mRNA, thus perturbing the mRNA-tRNA codon-anticodon interaction.