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Gene Review

blaI  -  BlaI

Staphylococcus aureus

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Disease relevance of blaI


High impact information on blaI

  • An operator DNA-protein complex observed with crude cell lysates from repressed cells, indistinguishable from that observed with purified BlaI, was eliminated by induction of the beta-lactamase operon [1].
  • BlaI binds with similar affinity to the two regions and to the related sequence upstream of the mec gene found in methicillin-resistant strains of S. aureus, providing physical evidence for the cross-talk previously observed between these systems [1].
  • A change from a lysine in the N-terminus of BlaI to an alanine or deletion of the C-terminal 23 amino acids severely reduces its DNA-binding ability, demonstrating the functional importance of both the N- and C-termini [1].
  • The values generated for wild-type repressors were compared to those in 26 isolates containing mecI mutations. mecA transcription appeared to be repressed only by BlaI in isolates with mecI nonsense and frameshift mutations [3].
  • DMS protection assays of BlaI binding to the bla operator in vitro and in vivo gave similar results so that it is tentatively concluded that the in vitro results are an accurate reflection of the in vivo situation [4].

Chemical compound and disease context of blaI


Biological context of blaI

  • Antisera prepared against purified MecI and against purified BlaI were used in Western blots which showed that MecI repressed the synthesis of BlaI in these diploids [5].
  • BlaI binds to two separate dyads but neither copper-phenanthroline footprinting nor dimethyl sulphate (DMS) methylation protection assays produced any evidence of a change in the geometry of the DNA between the two dyads [4].
  • MecI and BlaI can bind to both operator DNA sequences [6].

Analytical, diagnostic and therapeutic context of blaI


  1. Studies of the repressor (BlaI) of beta-lactamase synthesis in Staphylococcus aureus. Gregory, P.D., Lewis, R.A., Curnock, S.P., Dyke, K.G. Mol. Microbiol. (1997) [Pubmed]
  2. The fate of the BlaI repressor during the induction of the Bacillus licheniformis BlaP beta-lactamase. Filée, P., Benlafya, K., Delmarcelle, M., Moutzourelis, G., Frère, J.M., Brans, A., Joris, B. Mol. Microbiol. (2002) [Pubmed]
  3. Quantitation of mecA transcription in oxacillin-resistant Staphylococcus aureus clinical isolates. Rosato, A.E., Craig, W.A., Archer, G.L. J. Bacteriol. (2003) [Pubmed]
  4. Studies of the operator region of the Staphylococcus aureus beta-lactamase operon. Clarke, S.R., Dyke, K.G. J. Antimicrob. Chemother. (2001) [Pubmed]
  5. MecI represses synthesis from the beta-lactamase operon of Staphylococcus aureus. Lewis, R.A., Dyke, K.G. J. Antimicrob. Chemother. (2000) [Pubmed]
  6. Structure of the MecI repressor from Staphylococcus aureus in complex with the cognate DNA operator of mec. Safo, M.K., Ko, T.P., Musayev, F.N., Zhao, Q., Wang, A.H., Archer, G.L. Acta Crystallograph. Sect. F Struct. Biol. Cryst. Commun. (2006) [Pubmed]
  7. Transcription of the gene mediating methicillin resistance in Staphylococcus aureus (mecA) is corepressed but not coinduced by cognate mecA and beta-lactamase regulators. McKinney, T.K., Sharma, V.K., Craig, W.A., Archer, G.L. J. Bacteriol. (2001) [Pubmed]
  8. The signal transducer (BlaRI) and the repressor (BlaI) of the Staphylococcus aureus beta-lactamase operon are inducible. Clarke, S.R., Dyke, K.G. Microbiology (Reading, Engl.) (2001) [Pubmed]
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