Disease relevance of mrcB

• In this paper, we have analyzed the expression of ponB (mrcB), the structural gene for pbp 1b, and the relation among the three forms of pbp 1b in ponB strains lysogenyzed by lambda 540 (ponB+) recombinant bacteriophages [1].
• We report that chlorobiphenyl vancomycin analogues that are incapable of binding substrates nevertheless inhibit E. coli PBP1b, which shows that these compounds interact directly with the enzyme [2].

High impact information on mrcB

• We have identified transglycosylase assay conditions that enable kinetic analysis of inhibitors and have examined the inhibition of Escherichia coli penicillin-binding protein 1b (PBP1b) by moenomycin as well as by various glycopeptides [2].
• We have also found that moenomycin is not competitive with respect to the lipid II substrate of PBP1b, as has long been believed [2].
• These results strongly suggest that the periplasmic domain of PBP 1B associates with membranes independent of its amino terminal transmembrane region [3].
• Twelve amino acids, comprised of the consensus thrombin cleavage site (LVPR decreases GS) and flanking glycine residues, were inserted into PBP 1B just past its putative transmembrane segment [3].
• Cleavage of the protein was dependent upon the presence of the thrombin cleavage site, and the thrombin-cleaved protein (PBP 1Bper) displayed an identical affinity for [14C] penicillin G binding as wild-type PBP 1B and uncleaved PBP 1B-GT/H6 [3].

Chemical compound and disease context of mrcB

• A fragment from the ponB region of the Escherichia coli chromosome comprising the promoterless sequence encoding penicillin-binding protein 1B (PBP 1B) has been cloned in a broad-host-range expression vector under the control of the kanamycin resistance gene promoter present in the vector [4].

Biological context of mrcB

• This paper reports the sequence of the active site peptide of penicillin-binding protein 1b from Escherichia coli [5].
• Expression plasmids allowing the production of native PBP1B or of PBP1B variants with an inactive transpeptidase or transglycosylase domain or both were constructed [6].
• Moreover, we have shown by alanine-stretch-scanning mutagenesis that (i) residues R(11) to G(13) are major determinants for correct translocation and folding of PBP1b and that (ii) the specific interactions involving the full-length PBP1b can be ascribed to the first six residues at the N-terminal end of the cytoplasmic domain [7].
• The mutation, originally isolated in a strain with a high dosage of PBP1B, could also suppress the pbpB(Ts) phenotype when a single copy of the ponB gene was introduced [8].
• The kinetics of the reaction of purified penicillin-binding protein 1b gamma from Escherichia coli with cephalosporins suggest that the enzyme exists in two kinetically distinct conformations that are in slow equilibrium [9].

Anatomical context of mrcB

• These results indicated that PBP 1B of E. coli is compatible with the cytoplasmic membrane environment of unrelated bacterial species and support the idea that interspecific transfer of mutated alleles of genes coding for PBPs could potentially be an efficient spreading mechanism for intrinsic resistance to beta-lactams [4].

Associations of mrcB with chemical compounds

• Moenomycin-mediated affinity purification of penicillin-binding protein 1b [10].

Analytical, diagnostic and therapeutic context of mrcB

• Purified penicillin-binding protein 1b was labeled with [14C]penicillin G, digested with trypsin, and partially purified by gel filtration [5].
• The use of several methods of immunoelectron microscopy provided the first unequivocal evidence for localization of PBP 1b at membrane adhesion sites [11].
• Topology of penicillin-binding protein 1b of Escherichia coli and topography of four antigenic determinants studied by immunocolabeling electron microscopy [12].
• Western blotting (immunoblotting) revealed PBP 1b in most of the isolated membrane fractions; however, the highest label density was found in membrane fractions of intermediate density, supporting the suggestion of an increased concentration of PBP 1b in the membrane adhesion zones [11].
• This binding has been employed to isolate PBP 1b by affinity chromatography [10].

References