| Popis: |
Ethidium bromide (ETB) has been bound to the 30 S ribosomal subunits of both a streptomycin (Sm-CHO) sensitive and resistant strain of E. coli. The fluorescent intensity of the complex ETB – 30 S sensitive subunit is higher than that of the complex ETB – 30 S resistant subunit. When the 30 S sensitive subunit is previously treated with Sm-CHO, the intensity of the ETB – 30 S sensitive subunit complex is reduced. In contrast, the pretreatment of the 30 S resistant subunit by Sm-CHO does not affect the fluorescence of the dye complex. In addition no perturbation of the fluorescent complexes can be noted when either the 30 S resistant or 30 S sensitive subunit was pretreated with streptomycine oxime (Sm-CH=NOH), a biologically inactive derivative of Sm-CHO. These results indicate that the accessibility of the dye to the base-paired region of the 16 S RNA, the target of ETB, has been modified as resistance is conferred to the 30 S subunit.The modification of the quaternary structure of the 30 S resistant subunits as shown by fluorescence is similar to the Sm-CHO modification of the pretreated 30 S sensitive subunit. |
