Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.3.44 (P-glycoprotein)
 13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A Staphylococcus epidermidis plasmid conferring inducible resistance to 14-membered ring macrolides and type B streptogramins has been analysed and the DNA sequence of the gene responsible for resistance determined. A single open reading frame of 1.464 kbp, preceded by a complex control region containing a promoter and two ribosomal binding sites, was identified. The deduced sequence of the 488-amino-acid protein (MsrA) revealed the presence of two ATP-binding motifs homologous to those of a family of transport-related proteins from Gram-negative bacteria and eukaryotic cells, including the P-glycoprotein responsible for multidrug resistance. In MsrA, but not these other proteins, the two potential ATP-binding domains are separated by a Q-linker of exceptional length. Q-linkers comprise a class of flexible interdomain fusion junctions that are typically rich in glutamine and other hydrophilic amino acids and have a characteristic spacing of hydrophobic amino acids, as found in the MsrA sequence. Unlike the other transport-related proteins, which act in concert with one or more hydrophobic membrane proteins, MsrA appears to function independently when cloned in a heterologous host (Staphylococcus aureus RN4220). MsrA might, therefore, interact with and confer antibiotic specificity upon other transmembrane efflux complexes of staphylococcal cells. The active efflux of [14C]-erythromycin from cells of S. aureus RN4220 containing msrA has been demonstrated.
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PMID:Inducible erythromycin resistance in staphylococci is encoded by a member of the ATP-binding transport super-gene family. 223 55

GG918, a synthetic inhibitor of P-glycoprotein-mediated mammalian tumour multidrug resistance, was found to be equipotent to reserpine in enhancing the in vitro activity of norfloxacin and ciprofloxacin against strains of Staphylococcus aureus expressing distinct efflux-related multidrug resistance pumps. Four- to eight-fold reductions in MICs of these fluoroquinolones were observed for SA-1199B, a strain that overexpresses NorA (the major S. aureus multidrug transporter), and SA-K2068, which possesses a multidrug efflux-related pump distinct from NorA. Neither inhibitor potentiated the activity of newer fluoroquinolones such as levofloxacin or moxifloxacin by more than two-fold, and this effect was observed only in SA-1199B and SA-K2068. GG918 and reserpine exposure resulted in two- to four-fold reductions in norfloxacin and ciprofloxacin MICs in a fluoroquinolone-susceptible control strain and in strains expressing the MsrA and TetK proteins, which mediate efflux-related resistance to macrolides and tetracyclines, respectively, suggesting inhibition of as yet uncharacterized pumps for which norfloxacin and ciprofloxacin are substrates. In the MsrA- and TetK-expressing strains no more than a two-fold augmentation of erythromycin or tetracycline activity was observed with either inhibitor, suggesting minimal, if any, inhibitory activity against these efflux proteins. Using GG918 as a lead compound, a structure-activity evaluation may reveal a more potent and broader spectrum inhibitor of S. aureus antibiotic efflux pumps.
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PMID:A novel inhibitor of multidrug efflux pumps in Staphylococcus aureus. 1249 82