Binding streptomycin

Resistance to aminoglycosides arises from several mechanisms, the most important being the production of enzymes (plasmid controlled) that inactivate the drug by acetylation, phosphorylation or adenylation. Other mechanisms are the alterations of the envelope to prevent drug access and alteration of the binding site on the 30S subunit so that the drug does not bind (streptomycin only). 

Intestinal mucus, which contains the polysaccharide mucin, can avidly bind streptomycin and dihydrostreptomycin (E. Nelson et al, unpublished data). This binding may contribute to the... 

Alteration in binding site Streptomycin Protein S12 component of 30S ribosomal subunit determines sensitivity or resistance... 

Chloroplast protein synthesis is controlled largely at the post-transcriptional level [20,21] and can be repressed by the inclusion of antibiotics such as streptomycin in the sprouting medium. Streptomycin binds to the 16S rRNA and causes the ribosome to misread the mRNA sequence, producing incorrect and non-functional proteins [22]. 

Ramakrishnan and co-workers 3-A crystal structures of two different aminoglycosides (paromomycin and streptomycin) bound to the 30S subunit laid to rest much of the debate concerning the binding mode of aminoglycoside antibiotics. Paromomycin was found bound to the major groove of helix 44 (H44), confirming mutagenesis studies that had been carried out previously. ... 

Streptomycin binds with specific proteins (S12) on 30 S subunits of ribosomes. A change in this protein as a result of a mutation makes the ribosomes unable to bind with streptomycin, which makes the organism resistant. Mutational resistance to streptomycin occurs frequently. Gentamicin, tobramycin, netilmicin, and amikacin bind with many regions on both subunits of the ribosomes, and therefore mutational resistance to them is not common. 

Streptomycin and other aminoglycosides inhibit bacterial protein synthesis by binding... 

All aminoglycosides act by inhibiting protein synthesis of bacteria by directly combining with ribosomes. They penetrate the outer cytoplasmic membrane and inhibit protein synthesis. Streptomycin combines with the bacterial 30S ribosomes and inteferes with the mRNA-ribosome combination. Other aminoglycosides bind to additional sites on SOS subunit as well as to 30S-50S interface. 

Inside the cell, aminoglycosides bind to specific 30S-subunit ribosomal proteins (S12 in the case of streptomycin). Protein synthesis is inhibited by aminoglycosides in at least three ways (Figure 45-3) (1) interference with the initiation complex of peptide formation (2) misreading of mRNA, which causes incorporation of incorrect amino acids into the peptide and results in a nonfunctional or toxic protein and (3) breakup of polysomes into nonfunctional monosomes. These activities occur more or less simultaneously, and the overall effect is irreversible and lethal for the cell. 

Streptomycin Prevents bacterial protein synthesis by binding to the S12 ribosomal subunit (see also Chapter 45) Bactericidal activity against susceptible mycobacteria Used in tuberculosis when an injectable drug is needed or desirable and in treatment of drug-resistant strains IM, IV renal clearance (half-life 2.5 h) administered daily initially, then 2 x week Toxicity Nephrotoxicity, ototoxicity... 

An indirect competitive ELISA has been also developed for the determination of streptomycin and dihydrosticptomyciri in milk (24). Prior to the analysis, the milk sample was skimmed and treated with oxalic acid. The antiserum was raised in rabbits using streptomycin linked to a bacterial protein as the antigen. To perform the test, microtiter plates were coated with streptomycin, and antiserum and milk samples were mixed to be added in the wells where they were incubated for 1 h. Depending on the amount of residues in the sample, more or less antibody remained available for binding to the streptomycin coat. A pig antirabbit antibody-enzyme conjugate was subsequently added and incubated for 90 min. Using a suitable substrate, streptomycin and dihydrostreptomycin could be detected down to 1.6 ppb, whereas quantification could be made possible up to 100 ppb when samples were used undiluted. 

The glycoside/aminoglycoside antibiotics, like the macrolides, exert a bacteriostatic effect due to selective inhibition of bacterial protein synthesis, with the exception of novobiocin (26). The compounds neomycin (27), spectinomycin (28) and streptomycin (29) bind selectively to the smaller bacterial 30S ribosomal subunit, whilst lincomycin (30) binds to the larger 50S ribosomal subunit (cf. macrolides). Apramycin (31) has ribosomal binding properties, but the exact site is uncertain (B-81MI10802). Novobiocin (26) can inhibit nucleic acid synthesis, and also complexes magnesium ion, which is essential for cell wall stability. 

The aminoglycoside antibiotics streptomycin (Box 20-B),c d u v the neomycins,w paromomycin (see drawing below),c x z gentamycin,aa and kanamycin have one structural unit in common. They often bind to 16S ribosomal RNA in the decoding center. 

Streptomycin can also be chemically crosslinked to 16S RNA,66 and several aminoglycoside antibiotics including streptomycin and spectinomycin bind... 

Diluted antibody solutions can be reused multiple times They should be stored at 4°C after additional aliquots of penicillin/streptomycin and sodium azide have been added Some workers believe that the amount of nonspecific (background) staining on Western blots diminishes as antibody solutions are reutilized Antibody solutions are discarded or supplemented with additional antibody when the intensity of the specific signal begins to diminish 10. Choice of wash buffer after incubation with primary antibody 2M urea is included m the suggested wash buffer to diminish nonspecific binding. Alternatively, some... 

A great many antibiotic inhibitors of ribosome function belong to the class known as aminoglycoside antibiotics. Of these, streptomycin is the best known and the best investigated. Streptomycin binding produces a variety of... 

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