ISSN:
1365-2958
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
,
Medicine
Notes:
Prediction studies, conformational analyses and membrane-topology mapping lead to the conclusion that the penicillin sensory transducer, BlaR, involved in the inducibility of β-lactamase synthesis in Bacillus licheniformis, is embedded in the plasma membrane bilayer via four transmembrane segments TM1–TM4 that form a four-α-helix bundle. The extracellular 262-amino-acid-residue polypeptide, S340–R601, that is fused at the carboxy end of TM4, possesses the amino acid sequence signature of a penicilloyl serine transferase. It probably functions as penicillin sensor. As an independent entity, this polypeptide behaves as a high-affinity penicillin-binding protein. As a component of the full-size BlaR, it adopts a different conformation presumably because of interactions with the extracellular 63-amino-acid-residue P53–S115 loop that connects TM2 and TM3. Reception of the penicillin-induced signal requires a precise conformation of the sensor but it does not involve penicilloylation of the serine residue S402 of motif STYK. Signal transmission through the plasma membrane by the four-α-helix bundle may proceed in a way comparable to that of the aspartate receptor, Tar. Signal emission in the cytosol by the intracellular 189-amino-acid-residue Y134–K322 loop that connects TM3 and TM4, may proceed via the activation of a putative metallopeptidase.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1046/j.1365-2958.1997.2761642.x
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