Question

why does streptomycin affect mito handrail ribosomes of fungi?

Answer 1

Streptomycin belongs to aminoglycoside family of antibiotics and produced by Streptomyces griseus. Streptomycin binds with 30S ribosomal subunit and inhibits the initiation and elongation process during protein synthesis. Streptomycin binds irreversibly with specific proteins of 30S-subunit and 16S rRNA. Mainly Streptomycin interacts with four nucleotides of 16S rRNA and one amino acid of protein S12. This interaction interferes with decoding site of 16S rRNA of 30S subunit. Consequently, this interferes with initiation complex, misreading of mRNA due to this incorrect amino acids are inserted into the polypeptide therefore, nonfunctional or toxic peptides form. When this nonfunctional or toxic peptides from it breaks the polysomes into nonfunctional monosomes. Finally streptomycin inhibit the protein synthesis by this mechanism.

As we know that Streptomycin acts on 30S ribosome, this ribosome subunit found only in prokaryotes and mitochondria of eukaryotes e.g., fungi. Since, mitochondria of fungi have 30S subunit of ribosome, therefore streptomycin affect mitochondrial ribosomes of fungi by above mechanism.