Disease relevance of ftsI

• We show here that only four amino-acid substitutions need to be introduced into PBP 3 of E. coli to produce a strain possessing substantial levels of resistance to a wide variety of cephalosporins [1].
• After infection with this hybrid phage, penicillin-binding protein 3 was overproduced and incorporated into the E. coli inner membrane [2].
• Alterations affecting similar regions of Escherichia coli PBP3 and Neisseria gonorrhoeae PBP2 from beta-lactam-resistant strains are known [3].
• The fold adopted by the R71-V577 polypeptide of PBP3 has been modelled by reference to the corresponding R76-S634 polypeptide of the class B Streptococcus pneumoniae PBP2x [4].
• Similarly, CFP showed high affinity for Pseudomonas aeruginosa PBP-3, -1A, -1B, -2, and -4, in descending order [5].

High impact information on ftsI

• The Escherichia coli septum-specific penicillin-binding protein 3 (PBP3) forms a complex with other enzymes involved in murein metabolism, suggesting a centrally located transmembrane complex capable of splicing multiple new strands of peptidoglycan into the cell wall [6].
• We also show that transfer of the gene encoding the resistant PBP 3 from the chromosome to a plasmid could result in the spread of intrinsic resistance not only to other strains of E. coli but also to other enterobacterial species [1].
• Changes in E. coli morphology (elongation), observed just before bacteriolysis, were consistent with early predominant inactivation of PBP3 [7].
• The inhibition of septation was probably due to interference of the function of the wild-type penicillin-binding protein 3 in cell division by the enzymatically inactive thiol-enzyme, and this implies that penicillin-binding protein 3 acts as part of a complex in vivo [8].
• The active site serine residue of penicillin-binding protein 3 of Escherichia coli that is acylated by penicillin (Ser-307) has been converted to a cysteine residue using a simple and efficient two primer method of site-directed mutagenesis [8].

Chemical compound and disease context of ftsI

• However, all fusions that contained greater than or equal to 36 residues of PBP3 provided single cells of E. coli with substantial levels of resistance to ampicillin, indicating that the beta-lactamase moieties of these fusion proteins were translocated to the periplasm [9].
• The results indicate that, similar to their counterparts in Escherichia coli, PBP2 and PBP3 are the lethal targets of amdinocillin and furazlocillin, respectively [10].
• Induction of lysis of two E. coli mutants containing either a thermosensitive penicillin-binding protein (PBP) 2 or 3 by relatively PBP 3-specific (aztreonam) and PBP 2-specific (amdinocillin) antibiotics indicated that inhibition of only PBPs 2 and 3 can cause lysis [11].
• In the piperacillin and azlocillin series, there was good binding to PBP 3 of E. coli (0.1 microgram/ml) and PBPs 1, 2, and 3 of S. aureus (approximately 1 microgram/ml) [12].
• The affinity of DQ-2556 to PBP 3 of E. coli, which participates in septum formation, as suggested by morphological observation, was two times greater than that of ceftazidime [13].

Biological context of ftsI

• The translated amino acid sequence demonstrated 45% identity and had a total of 66% conserved amino acids relative to the Escherichia coli PBP3 [14].
• PBP 3 had an unusually high k(2)/K' value relative to other PBPs for acylation with penicillin (7.7 x 10(5) M(-1) s(-1)) at pH 8.5 at 25 degrees C and hydrolyzed bound antibiotic very slowly (k(3) < 4.6 x 10(-5) s(-1), t(1/2) > 230 min) [15].
• The control of PBP3 activity during the cell cycle is briefly discussed [16].
• Restriction endonuclease mapping of one of the recombinant cosmids, pLB100, was performed to facilitate subsequent subcloning of the gene(s) responsible for the altered penicillin-binding protein 3 (a and b) binding phenotype [17].
• A Haemophilus influenzae strain (T-1,3) possessing clinical beta-lactam resistance due to altered penicillin-binding protein 3 was used to construct a recombinant cosmid gene bank in Escherichia coli [17].

Anatomical context of ftsI

• All penicillin-binding proteins--except penicillin-binding protein 3, which is found almost exclusively in the cytoplasmic membrane and is involved in septum formation--are also found in gradient fractions corresponding to the outer membrane [18].
• The in vivo activity of PBP3 also depends on the M-1-to-E-56 amino-terminal module which encompasses the cytosol, the membrane, and the periplasm and which functions as a noncleaved pseudo-signal peptide [19].
• Yme1p, a yeast mitochondrial protein, affects the rate of DNA escape from mitochondria to the nucleus and the Escherichia coli FtsH protein is apparently involved in the post-translational processing of PBP3, a protein necessary for septation during cell division [20].
• These compounds have maintained their high affinity for the essential PBP 3, typical of the third generation cephalosporins and have acquired an improved ability to cross the outer membranes of Gram-negative bacteria [21].

Associations of ftsI with chemical compounds

• In addition, FtsZ rings are able to assemble in newborn cells in the presence of cephalexin, suggesting that newborn cells contain a site at which FtsZ can assemble (the nascent division site) and that the transpeptidase activity of FtsI is not required for assembly of FtsZ at these sites [22].
• By using low concentrations of the beta-lactams cephalexin and piperacillin to specifically inhibit FtsI (PBP3), an enzyme that synthesizes peptidoglycan at the division septum, we show that FtsZ ring constriction requires the transpeptidase activity of FtsI [22].
• In the presence of furazlocillin or other beta-lactams with a specificity for penicillin-binding protein 3 which normally cause filamentation, bulges were formed prior to rapid bacteriolysis [23].
• In contrast to subunits of the divisome, PBP2 failed to localize at mid-cell when PBP3 was inhibited by the specific antibiotic aztreonam [24].
• The coding region for mature TEM beta-lactamase was fused after the signal peptide and aminoterminal portion of the coding region of a weakly expressed periplasmic protein, PBP3*. The resultant plasmid was mutagenized and transformants expressing increased levels of ampicillin resistance were selected [25].

Other interactions of ftsI

• The ftsI-encoded multimodular class B penicillin-binding protein 3 (PBP3) is a key element of the cell septation machinery of Escherichia coli [19].
• Saturation of a single PBP by cefsulodin (PBP 1s), mecillinam (PBP 2), and aztreonam (PBP 3) resulted in a slow rate of killing (2.5-, 1.5-, and 0.8-log-unit decreases in the number of CFU per milliliter, respectively, in 6 h) [26].

Analytical, diagnostic and therapeutic context of ftsI

• Inactivation of FtsI inhibits constriction of the FtsZ cytokinetic ring and delays the assembly of FtsZ rings at potential division sites [22].
• From these plasmid-carrying strains, PBP-1a and -1b were purified by ampicillin-Sepharose affinity chromatography and PBP-3 by cephalexin-Sepharose affinity chromatography [27].
• We conclude (i) that immunofluorescence microscopy can be used to localize proteins whose abundance is as low as approximately 100 molecules per cell; and (ii) that spatial and temporal regulation of FtsI activity in septum formation is achieved, at least in part, by timed localization of the protein to the division site [28].
• FtsI has been estimated to be present at about 100 molecules per cell, well below the detection limit of immunoelectron microscopy [28].
• The direct protein-protein interaction between purified PBP3 and PBP1B was characterized in vitro by surface plasmon resonance [29].

References