Biomedical subjects

S Handwerger

Publications and source records attributed to S Handwerger.

At least 19 recordsLinked to original sources

PubMed2000

Activator protein-2 regulates human placental lactogen gene expression.

DNase I footprint analysis of the human placental lactogen-A (hPL-A) promoter using nuclear extracts from purified human trophoblast cells and BeWo choriocarcinoma cells revealed five protected regions within the proximal 325 bp. Two of the protected regions, FP4 (-289--267) and FP5 (-167--154), are homologous to regions on the human growth hormone (hGH) promoter that bind transcription factors AP-2 and/or NFI. Competitive gel shift assays and supershift assays indicated that FP4 forms complexes with activator protein-2 (AP-2) and nuclear factor I (NFI), while FP5 forms a complex with AP-2 alone. In transient transfection studies in human trophoblast cells, hPL promoter constructs containing point mutations in the AP-2 binding sites of FP4 and/or FP5 were 60-80% less active than plasmids containing the wild-type promoter. A mutation in the NFI binding site of FP4, however, had little effect on promoter activity in these cells. Overexpression of AP-2 in HepG2 cells co-transfected with the wild-type hPL promoter resulted in a significant increase in promoter activity. Taken together, these findings suggest a critical role for AP-2 in the regulation of hPL gene expression.

Base Sequence↗

PubMed2000

Mitogen-activated protein kinase activates human placental lactogen-B enhancer by an NF-IL6-dependent pathway.

Computer analysis of the human placental lactogen-B (hPL-B) enhancer reveals two putative binding sites for the transcription factor NF-IL6, but the role of NF-IL6 in the regulation of the enhancer is unknown. Using gel mobility shift and supershift assays, we demonstrated that NF-IL6 binds to both enhancer sites. Transient transfection studies indicated that the transcription factor NF-IL6 stimulates hPL-B enhancer activity by 4.4-fold in primary cultures of human trophoblast cells and by 32.0- and 8.4-fold in JAR and BeWo choriocarcinoma cells, respectively. Overexpression of MEK (mitogen-activated protein [MAP] kinase kinase), which is known to stimulate phosphorylation of NF-IL6, induced a 3.6-fold increase in hPL-B enhancer activity. The induction by MEK was completely inhibited by an expression plasmid for a dominant/negative mutant of NF-IL6 or by mutation of the NF-IL6 binding sites on the enhancer. PD98059, an inhibitor of MEK, inhibited hPL release from cultured trophoblast cells by about 50%. Taken together, these results indicate that MAP kinase stimulates the hPL-B enhancer by an NF-IL-6-dependent pathway.

CCAAT-Enhancer-Binding Proteins↗

PubMed2000

The roles of placental growth hormone and placental lactogen in the regulation of human fetal growth and development.

The human growth hormone (hGH)/human placental lactogen (hPL) gene family, which consists of two GH and three PL genes, is important in the regulation of maternal and fetal metabolism and the growth and development of the fetus. During pregnancy, pituitary GH (hGH-N) expression in the mother is suppressed; and hGH-V, a GH variant expressed by the placenta, becomes the predominant GH in the mother. hPL, which is the product of the hPL-A and hPL-B genes, is secreted into both the maternal and fetal circulations after the sixth week of pregnancy. hGH-V and hPL act in concert in the mother to stimulate insulin-like growth factor (IGF) production and modulate intermediary metabolism, resulting in an increase in the availability of glucose and amino acids to the fetus. In the fetus, hPL acts via lactogenic receptors and possibly a unique PL receptor to modulate embryonic development, regulate intermediary metabolism and stimulate the production of IGFs, insulin, adrenocortical hormones and pulmonary surfactant. hGH-N, which is expressed by the fetal pituitary, has little or no physiological actions in the fetus until late in pregnancy due to the lack of functional GH receptors on fetal tissues. hGH-V, which is also a potent somatogenic hormone, is not released into the fetus. Taken together, studies of the hGH/hPL gene family during pregnancy reveal a complex interaction of the hormones with one another and with other growth factors. Additional investigations are necessary to clarify the relative roles of the family members in the regulation of fetal growth and development and the factors that modulate the expression of the genes.

Embryonic and Fetal Development↗

PubMed1999

N5 endometrial stromal cell line: a model system to study decidual prolactin gene expression.

Prolactin gene expression in extrapituitary tissues, such as decidua and lymphocytes, is regulated by a distinct promoter approximately 6 kb upstream of the pituitary prolactin gene transcription start site. Here we describe studies in a human endometrial stromal cell line, N5, that was immortalized by transfection with an SV40 mutant and which expresses the prolactin gene driven by the extrapituitary promoter. The N5 cells have phenotypic features of primary cultures of decidualized human endometrial stromal cells and secrete low levels of prolactin and insulin-like growth factor binding protein-1 (IGFBP-1), both of which are markers of decidualized endometrial stromal cells. As in primary cultures of endometrial stromal cells, treatment of N5 cells with progesterone and estradiol alone or in combination with prostaglandin E2 stimulated the synthesis and release of prolactin. Transient transfection of the N5 cells with an expression vector containing - 2927/ + 66 bp of the decidual prolactin promoter coupled to a luciferase reporter gene resulted in a 20 to 25-fold increase in luciferase activity, a magnitude similar to that which occurs in primary cultures of endometrial stromal cells decidualized in vitro by treatment with progesterone and estradiol. Luciferase expression levels were similar in untreated N5 cells and N5 cells treated with progesterone and estradiol. Taken together, these results indicate that the N5 human endometrial stromal cell line has phenotypic characteristics of normal decidualized stromal cells and is a useful model to study regulation of decidual prolactin gene expression.

Bucladesine↗

PubMed1999

Pre-beta-HDL stimulates placental lactogen release from human trophoblast cells.

To examine whether pre-beta-high-density lipoprotein (HDL) may be involved in regulation of human placental lactogen (hPL) release, pre-beta-HDL was isolated from term pregnancy serum, and the effect of purified pre-beta-HDL on hPL release from trophoblast cells was examined after 1 h of exposure. Pre-beta-HDL stimulated a dose-dependent increase in hPL release with half-maximal stimulation at a dose of 300-400 microgram/ml, which is within the normal physiological range during pregnancy. Analysis of pre-beta-HDL and alpha-HDL in serum from pregnant women at different stages of gestation (determined by Western blot analysis) indicated that the pre-beta-HDL-to-alpha-HDL ratio increased linearly after the 10th week of gestation (r = 0.88, P < 0.001), reaching a maximum sixfold greater than that of nonpregnant women. The increase in serum pre-beta-HDL during pregnancy paralleled that of plasma hPL concentrations (r = 0.93, P < 0.001). Two-dimensional electrophoresis indicated that the increase in pre-beta-HDL was due primarily to an increase in pre-beta1-HDL and pre-beta2-HDL, two of the three forms of pre-beta-HDL present in blood. These results suggest a role for pre-beta-HDL in the regulation of hPL expression during pregnancy.

Cells, Cultured↗

PubMed1999

Interleukin-2 inhibits the synthesis and release of prolactin from human decidual cells.

PRL is synthesized and released by several extrapituitary tissues, including decidualized endometrial stromal cells. As interleukin-2 (IL-2) stimulates the synthesis and release of pituitary PRL, and decidual stromal cells have receptors for IL-2, we examined whether IL-2 also regulates the release of decidual PRL. Exposure of primary cultures of human decidual cells (10(6) cells/well) from term pregnancies to IL-2 (50 ng/mL) inhibited PRL release beginning 48 h after exposure. The inhibition by IL-2 was dose dependent, and the maximal inhibition of PRL release after 5 days of exposure to IL-2 was 71.0 +/- 0.9% (mean +/- SE). IL-2, however, had no effect on decidual cell viability. The inhibitory effect of IL-2 on PRL release was secondary to inhibition of PRL synthesis. Decidualized human endometrial stromal cells transfected with 3 kb of the extrapituitary PRL (exon 1a) promoter coupled to a luciferase expression vector responded to IL-2 (10 ng/mL) with a significant decrease in luciferase activity. These findings strongly suggest that IL-2 inhibits the synthesis and release of decidual PRL and provide further support for a critical role of cytokines in the regulation of decidual PRL gene expression.

Cells, Cultured↗

PubMed1998

Apolipoprotein A-I stimulates human placental lactogen release by activation of MAP kinase.

Apolipoprotein A-I (apo A-I) stimulates human placental lactogen (hPL) release via protein kinase C (PKC)-dependent pathways. Since PKC has been shown to activate the MAP kinase cascade in other cell types, we examined the effect of two inhibitors of the MAP kinase cascade on apo A-I-induced hPL secretion and the effect of apo A-I on MAP kinase activity in human trophoblast cells. Apigenin (10 microM) and PD98059 (100 microM) inhibited apo A-I-induced hPL release by 94 and 73%, respectively. Moreover, apo A-I activated MAP kinase in a time- and dose-dependent manner. Activation of PKC by phorbol myristate acetate (PMA) stimulated MAP kinase activity, and down-regulation of PKC completely prevented apo A-I-stimulation of MAP kinase activity. Taken together, these results strongly suggest that activation of MAP kinase is involved in the intracellular mechanism of apo A-I-induced hPL release.

Apolipoprotein A-I↗

PubMed1998

Differential localization of heat shock proteins 90, 70, 60 and 27 in human decidua and placenta during pregnancy.

Little is known about the localization of heat shock proteins (HSPs) in the decidua and placenta during the course of normal pregnancy. In this study, we have examined the localization of the HSPs in decidual and placental tissues obtained from women during the first, second and third trimesters of pregnancy (five in each trimester) by immunohistochemistry using highly specific antisera. HSPs 90, 70, 60 and 27 were detected in decidual stromal cells during each trimester. The intensity of staining did not change during gestation for HSPs 60 and 27, whereas it decreased with advancing gestation for HSPs 90 and 70. HSPs 90 and 60 were localized primarily in the nucleus, whereas HSP 70 was present equally in the nucleus and the cytoplasm; HSP 27 was primarily in the cytoplasm. In the placenta, HSPs 90, 70 and 60 were localized in cytotrophoblast, syncytiotrophoblast, intermediate trophoblast, Hofbauer and endothelial cells. HSPs 90 and 60 were localized primarily in the nucleus, while HSP 70 was in the nucleus and the cytoplasm. In the placenta, HSP 27 was detected only in the intermediate trophoblast and syncytiotrophoblast cells and only in the first two trimesters. These results indicate that there are striking differences in the subcellular localization of HSPs in the decidua and the placenta during normal pregnancy.

Chaperonin 60↗

PubMed1997

Beta-adrenergic regulation of renin expression in differentiated U-937 monocytic cells.

Previous studies from our laboratories demonstrated that human decidual macrophages and peripheral mononuclear cells express renin. In the present study, we found that U-937 monocytes, induced to differentiate into macrophage-like cells by treatment with phorbol dibutyrate (PDBU), express renin mRNA and release renin (95%, of which is in the form of prorenin). Treatment of these PDBU-exposed cells with dibutyryl-cAMP (1 mM) caused a 20-fold increase in renin mRNA and a 10-fold increase in prorenin release. Forskolin (10 microM), an activator of adenylyl cyclase, and terbutaline (100 microM), a beta2-adrenergic agonist known to increase cAMP levels, also increased renin mRNA and prorenin release. The secretory response to terbutaline was potentiated by the type IV cyclic AMP-phosphodiesterase (PDE) inhibitor Ro 20-1724 (50 microM). Angiotensin II agonist inhibited the stimulatory effect of terbutaline on renin secretion as did the cytokines tumor necrosis factor-alpha and lipopolysaccharide plus interferon-gamma. Since other studies have shown that U-937 cells possess beta2-adrenergic receptors and express mainly the type IV PDE, the present findings strongly suggest that beta-adrenergic receptors in mononuclear cells are coupled to renin expression via the cAMP transduction pathway. The results support a possible role for the renin-angiotensin system in macrophage function and suggest potential autocrine regulatory mechanisms in prorenin expression.

4-(3-Butoxy-4-methoxybenzyl)-2-imidazolidinone↗

PubMed1997

Regulation of the human chorionic gonadotropin alpha- and beta-subunit promoters by AP-2.

Production of the placental hormone, chorionic gonadotropin (CG), increases dramatically as cytotrophoblasts fuse to form syncytiotrophoblasts. The CG alpha- and beta-promoters are both responsive to cAMP, although the kinetics of cAMP stimulation are different. In an effort to understand the mechanisms of coordinate induction of these genes, AP-2 binding sites were identified in the promoter regions of the alpha and CGbeta genes. AP-2 bound to the upstream regulatory element (-186 to -156 base pairs (bp)) in the alpha-promoter and to several different regions of the CGbeta promoter, including footprints 2 and 4B (FP2, -311 to -279 bp; FP4B, 221 to -200 bp). AP-2 antibodies induced supershifts of these complexes, confirming the identity of the protein-DNA complex. In JEG-3 cells, which contain abundant AP-2, mutations in these CGbeta AP-2 sites reduced basal activity and decreased cAMP stimulation. In AP-2-deficient Hep-G2 cells, co-transfection of AP-2 stimulated expression of the CGbeta promoter 10-20-fold, and the alpha-promoter was induced by 3-6-fold. Mutations that eliminate AP-2 binding to CGbeta FP4B reduced AP-2 stimulation by more than 80%, whereas mutations in FP2 reduced AP-2 stimulation by less than 50%. Analyses of AP-2 mutants revealed a requirement for the DNA binding/dimerization domain and the amino-terminal proline-rich and acid-rich transactivation domains for stimulation of the CGbeta promoter. Primary cultures of placental cytotrophoblasts were differentiated into syncytiotrophoblasts in vitro to examine AP-2 expression by reverse transcriptase-polymerase chain reaction. AP-2 mRNA levels increased by day 2 and continued to rise in parallel with a marked increase in alpha and CGbeta gene expression. We conclude that both the alpha and CGbeta promoters contain binding sites for AP-2 and suggest that this transcription factor provides a mechanism for coordinating the induction of these genes during placental cell differentiation.

Cell Nucleus↗

PubMed1997

Progesterone-dependent decidualization of the human endometrium is mediated by cAMP.

Progesterone is a key factor in regulating endometrial cell decidualization, but the signal transduction pathways involved in mediating the effects of progesterone are not known. A role of the cAMP pathway in decidualization has been suggested by in vitro studies demonstrating that cAMP agonists can stimulate decidualization, in the absence of sex steroids. In this article, we have used an in vitro culture model of progesterone-dependent decidualization of human endometrial stromal cells to examine whether progesterone-induced decidualization is associated with activation of the cAMP signal transduction pathway in which the prolactin gene expression is a marker of decidualization. Following a lag period of approx 3 d, progesterone induced prolactin secretion and elevated intracellular cAMP levels. By d 15, cAMP and prolactin levels were approx 10- and 60-fold greater, respectively, than those on d 3. Changes in cAMP levels showed a positive correlation with prolactin secretion. Prostaglandin E2 (PGE2), which enhances progesterone-dependent decidualization, also increased both prolactin secretion and cAMP levels approx two- to fourfold on d 15 compared with d 3, whereas PGE2 alone, which does not induce decidualization, did not stimulate prolactin secretion or intracellular cAMP accumulation. Conversely, all-trans retinoic acid, which attenuates progesterone-dependent decidualization, significantly (p < 0.05) decreased both prolactin secretion and cAMP levels. Furthermore, the protein kinase A (PKA) inhibitor, 8-bromoadenosine-3',5'-cyclic monophosphorothioate, significantly (p < 0.05) suppressed progesterone-dependent prolactin expression. Since activation of the PGE2 receptor subtype EP2 stimulates adenylate cyclase, reverse transcription-polymerase chain reaction (RT-PCR) analysis of endometrial cells was undertaken. Expression of EP2 mRNA was induced in cells treated with progesterone and estradiol alone or with PGE2, compared with untreated controls. The data suggest that the cAMP signal transduction cascade is activated during progesterone-dependent decidualization.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed1997

Comparative in-vitro activities of RP59500 (quinupristin/dalfopristin), CL 329,998, CL 331,002, trovafloxacin, clinafloxacin, teicoplanin and vancomycin against Gram-positive bacteria.

The in-vitro activities of five investigational antibiotics, RP59500 (a semisynthetic injectable streptogramin), CL 329,998 and CL 331,002 (two new glycylcyclines), trovafloxacin (a naphthyridone), and clinafloxacin (a dihalogenated quinolone), were examined and compared with those of minocycline, teicoplanin and vancomycin against 190 clinical isolates of Gram-positive cocci. The MICs for RP59500 against all isolates with the exception of Enterococcus faecalis were low. RP59500 was bactericidal against all except enterococcal isolates. CL 329,998 and CL 331,002 were significantly more active than minocycline against oxacillin-resistant Staphylococcus aureus (MIC90 0.25 versus 8 mg/L) and all enterococcal isolates (MIC90 0.125 versus 16 mg/L). Clinafloxacin was the most active agent against all staphylococcal isolates and was bactericidal. Trovafloxacin showed good activity against oxacillin-susceptible staphylococci and alpha-haemolytic streptococci (MIC90 < or = 0.125 mg/L). This study demonstrates the potential of the five investigational antibiotics as therapeutic agents for infections caused by Gram-positive cocci.

Anti-Bacterial Agents↗

PubMed1996

Human placental tissue expresses a novel 22.7 kDa apolipoprotein A-I-like protein.

Since apolipoprotein A-I (apo A-I) and HDL stimulate the expression of the placental hormone human placental lactogen (hPL), experiments were performed to determine whether the human placenta synthesizes apo A-I. Western blot analysis of a partially purified extract of human term placenta with an antiserum to human apo A-I yielded an immunoreactive band with an apparent mass of approximately 23.5 kDa, which is smaller than human plasma apo A-I (28 kDa). HPLC chromatography of the partially purified placental extract on a preparative reverse-phase C-18 column yielded two fractions that reacted to the apo A-I antiserum. The mass of both fractions by mass spectral analysis was 22 721 daltons, and N-terminal amino acid sequences were identical to the first four amino acids of apo A-I (Asp, Glu, Pro, Pro). The apo A-I-like protein was not a proteolytic product of apo A-I since Northern analysis of placental RNA with a 641 bp apo A-I cDNA fragment encoding most of the 5' region of the apo A-I mRNA detected a single band of 850 nt, which is smaller than the size of apo A-I mRNA (1100 nt). Placental mRNA, however, did not hybridize with a 3' apo A-I riboprobe, indicating that the 3' region of the apo A-I-like mRNA is different from that of apo A-I mRNA. Differences in the mRNAs were confirmed by S1 nuclease analysis of placental RNA with a cDNA probe that included the 3' end of the apo A-I cDNA and by RT-PCR analysis with a series of oligonucleotide primers that span the entire cDNA for apo A-I. Since there is only a single apo A-I gene in the human genome, these findings strongly suggest that human placental tissue expresses a novel 22.7 kDa apo A-I-like protein (ALP) that results from alternative splicing of the apo A-I primary transcript.

Apolipoprotein A-I↗

PubMed1996

Mobilization of vancomycin resistance by transposon-mediated fusion of a VanA plasmid with an Enterococcus faecium sex pheromone-response plasmid.

A striking feature of recent outbreaks of vancomycin-resistant (VmR) enterococci is the apparent horizontal dissemination of resistance determinants. The plasmids pHKK702 and pHKK703 from Enterococcus faecium clinical isolate R7 have been implicated in the conjugal transfer of VmR. pHKK702 is a 41-kb plasmid that contains an element indistinguishable from the glycopeptide-resistance transposon Tn1546. pHKK703 is an approx. 55-kb putative sex pheromone-response plasmid that is required for conjugative mobilization of pHKK702. During experiments in which strain R7 was used as a donor, a highly conjugative VmR transconjugant was isolated that formed constitutive cellular aggregates. Restriction analyses and DNA hybridizations revealed that the transconjugant harbored a single plasmid of approx. 92 kb and this plasmid (pHKK701) was composed of DNA from both pHKK702 and pHKK703. Results from DNA sequence analyses showed that a 39-kb composite transposon (Tn5506) from pHKK702 had inserted into pHKK703. The left end of Tn5506 contained a single insertion sequence (IS) element, IS1216V2, whereas the right end was composed of a tandem IS structure consisting of the novel 1065-bp IS1252 nested within an IS1216V1 element. Transposition of Tn5506 from pHKK702 to pHKK703 created an 8-bp target sequence duplication at the site of insertion and interrupted an ORF (ORFX) that was 91% identical to that of prgX, a gene proposed to negatively regulate sex pheromone response of the E.faecalis plasmid, pCF10. We propose that the interruption of ORFX by Tn5506 led to the constitutive cellular aggregation phenotype and thereby enhanced the efficiency with which VmR was transferred. Similar IS1216V-mediated transposition events may contribute to the horizontal spread of glycopeptide resistance among enterococci in nature.

Amino Acid Sequence↗

PubMed1996

Peptidoglycan composition of vancomycin-resistant Enterococcus faecium.

Muropeptide composition of peptidoglycan isolated from isogenic vancomycin-resistant and sensitive Enterococcus faecium strains was analyzed by reverse-phase high-performance liquid chromatography combined with amino acid and fast atom bombardment mass spectrometric analyses. Peptidoglycan of the sensitive and resistant strains was the same and was composed of tri- and tetrapeptides stem peptide subunits with or without aspartate or asparagine substitutions on the epsilon-amino group of the lysine residue. Thus, the synthesis of lactate-terminating peptidoglycan precursors in vancomycin-resistant E. faecium did not affect the chemical composition of peptidoglycan.

Amino Acids↗

PubMed1996

Persistence of vancomycin-resistant Enterococcus faecium gastrointestinal tract colonization in antibiotic-treated mice.

Colonization with vancomycin-resistant Enterococcus faecium (VREF) is strongly associated with previous antimicrobial therapy. The gastrointestinal (GI) tract appears to be the major reservoir for this organism. We used antibiotic-treated Swiss Webster mice to study GI tract colonization with a characterized strain of VREF (E. faecium 228). Mice were pretreated with antibiotics in their daily drinking water and inoculated with 10(9) colony-forming units (CFU) of E. faecium 228 by oral gavage. We were able to establish persistent colonization with high concentrations of E. faecium 228 (> 8.0 log10 CFU/g of feces) in animals treated with 5 mg/ml of streptomycin plus 1 mg/ml of cefotetan. RP 59500, a streptogramin antibiotic with good in vitro activity against VREF, was administered orally in mice (n = 8) colonized with E. faecium 228. After 14 days of treatment VREF was undetectable in feces of all treated mice (< 3.0 CFU/g). Seven days after discontinuation of RP 59500, VREF was present in the feces of all animals. VREF isolates recovered after treatment remained susceptible to RP 59500. Attempts to eradicate E. faecium 228 colonization by oral administration of a vancomycin-sensitive E. faecium strain (SF68) or Lactobacillus spp. were unsuccessful as long as animals continued to receive streptomycin and cefotetan. Recovery of E. faecium 228 from cultures of livers and gallbladders in some animals with persistent GI tract colonization suggests that the organisms may also colonize the hepatobiliary system.

Animals↗

PubMed1996

Interferon-gamma inhibits the synthesis and release of renin from human decidual cells.

Experiments were performed to examine the effect of interferon-gamma (IFN gamma) on the expression of renin by human uterine decidual cells and decidual macrophages. Exposure of a mixed population of decidual cells consisting of 80% decidualized stromal cells and 20% macrophages to IFN gamma for 4 days caused a dose-dependent inhibition of renin release beginning 2 days after exposure. Renin release on Day 4 was inhibited by a maximum of 83.9%, and the half-maximal effective dose of IFN gamma was 5 ng/ml (290 pM). The inhibition of renin release in response to IFN gamma was accompanied by a comparable inhibition of renin mRNA levels. In addition to inhibiting basal renin expression, IFN gamma potentiated the inhibitory effect of tumor necrosis factor alpha (TNF alpha) on renin expression. IFN gamma also inhibited basal renin release and potentiated the inhibitory effect of TNF alpha by highly purified populations of decidual stromal cells and decidual macrophages prepared by immunomagnetic separation with beads coupled to an anti-human leukocyte antigen (HLA-DR) antibody that binds macrophages but not stromal cells. Reverse transcription-polymerase chain reaction analysis showed that HLA-DR(+) cells express IFN gamma mRNA, and that both HLA-DR(+) and HLA-DR(-) cells express IFN gamma receptors. Since IFN gamma is expressed only by decidual macrophages, the results of this study strongly suggest that IFN gamma inhibits the expression of decidual renin by a paracrine action.

Base Sequence↗

PubMed1996

Altered peptidoglycan composition in vancomycin-resistant Enterococcus faecalis.

The muropeptide compositions of isogenic vancomycin-resistant and -susceptible Enterococcus faecalis strains were analyzed by reverse-phase high-performance liquid chromatography combined with amino acid analysis and fast atom bombardment mass spectrometry. Peptidoglycan of the susceptible strain contained pentapeptides as stem peptides, whereas peptidoglycan of the isogenic resistant strain was composed of muropeptides with tetrapeptide stem peptides. Despite the synthesis of lactate-terminating peptidoglycan precursors, no lactate-containing muropeptides were detected in peptidoglycan of the resistant strain. These findings indicate that either lactate-terminating precursors are not incorporated into peptidoglycan of the resistant strain or that the lactate residues are removed from peptidoglycan during synthesis.

Amino Acid Sequence↗