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Biomedical subjects

H C Wu

Publications and source records attributed to H C Wu.

At least 19 recordsLinked to original sources
PubMed1995

Ceramide reverses brefeldin A (BFA) resistance in BFA-resistant cell lines.

We have found that C6 ceramide, a cell-permeable ceramide analog, partially restored the brefeldin A (BFA) sensitivity in a BFA-resistant mutant of Vero cells (BER-40) and in the naturally BFA-resistant Madin-Darby canine kidney (MDCK) cells. Incubation of BER-40 and MDCK cells with low concentrations of C6 ceramide resulted in (i) a pronounced increase in BFA cytotoxicity as measured by the inhibition of [3H]thymidine incorporation and the inhibition of colony formation by BFA, (ii) a significant protection by BFA against ricin cytotoxicity, and (iii) an inhibition of bulk protein secretion by BFA in BER-40 and MDCK cells. Related sphingolipids including sphingosine, sphingomyelin, and lactosylceramide and other unrelated lipid second messengers such as arachidonic acid and 1,2-diacylglycerol did not elicit the protection of BER-40 and MDCK cells against ricin cytotoxicity by BFA. C6 ceramide was the most effective among the ceramides with different acyl chain lengths. Interestingly, dihydro-C6 ceramide, which lacks the trans double bond in the sphingoid base, had no effect. On the other hand, C6 ceramide did not enhance BFA sensitivity in BFA-sensitive Vero cells. The LD50 of C6 ceramide were similar in Vero and BER-40 cells. Fluorescence microscopic studies revealed that C6 ceramide induced the redistribution of beta-COP from the Golgi membranes to a more dispersed localization in both BFA-sensitive and BFA-resistant cell lines, mimicking the effect of BFA. Suboptimal concentration of C6 ceramide also restored the effect of BFA on the beta-COP distribution in BER-40 and MDCK cells. These results indicate that C6 ceramide restores the BFA sensitivity in BFA-resistant BER-40 and MDCK cells.

Animals↗
PubMed1995

Ilimaquinone inhibits the cytotoxicities of ricin, diphtheria toxin, and other protein toxins in Vero cells.

Ilimaquinone (IQ), a metabolite from sea sponges, has been shown to cause the breakdown of Golgi membranes into small vesicular structure and to inhibit protein transport without eliciting the retrograde transport of the Golgi enzymes to the endoplasmic reticulum [P. A. Takizawa, J. K. Yucel, B. Viet, D. J. Faulkner, T. Deerinck, G. Soto, M. Ellismann, and V. Malhotra, Cell (1993) 73, 1079-1090]. We have found that incubation of Vero cells with IQ inhibited the cytotoxicity of ricin in a dose-dependent manner. The inhibition was reversed upon the removal of IQ. Neither binding and internalization of 125I-ricin nor the translocation of ricin to the cytosol was affected by IQ. However, IQ significantly inhibited the recycling and degradation of internalized 125I-ricin. Preincubation with IQ also prevented the enhancement of ricin cytotoxicity by NH4Cl or nigericin. The inhibition of ricin cytotoxicity by IQ was observed in the presence of cycloheximide, indicating that de novo protein synthesis is not required for IQ-mediated protection of Vero cells from ricin cytotoxicity. In contrast to perinuclear distribution of TRITC-labeled ricin in Vero cells, TRITC-ricin appeared in numerous small vesicles dispersed throughout the cytoplasm in IQ-treated Vero cells. Double labeling with C6-NBD-ceramide and TRITC-labeled ricin showed that these ricin-containing vesicles were distinct from the IQ-induced breakdown product of the Golgi membranes. Like brefeldin A (BFA), IQ inhibited the cytotoxicities of abrin, modeccin, Pseudomonas toxin, and Shiga-like toxin in Vero cells. Unlike BFA, IQ also inhibited the cytotoxicity of diphtheria toxin (DT). Inhibition of DT cytotoxicity was the consequence of a decreased specific binding of the toxin in the IQ-treated cells.

Animals↗
PubMed1995

Protective effect of cell-permeable ceramide analogs against modeccin, ricin, Pseudomonas toxin, and diphtheria toxin.

We investigated the effects of various ceramide (Cer) analogs and related sphingolipids on the cytotoxicities of modeccin, ricin, Pseudomonas toxin, and diphtheria toxin in various cell lines. The most pronounced protective effect by C6Cer, a short-chain cell-permeable Cer analog, was observed in modeccin cytotoxicity in Vero, BER-40, and MDCK cells, whereas the cytotoxicity of diphtheria toxin was not affected by any of the ceramide analogs tested. C6Cer did not affect the binding and internalization of ricin and modeccin in Vero and BER-40 cells. C2Cer and C8Cer also protected against modeccin cytotoxicity, albeit less effectively than C6Cer. However, related sphingolipids including sphingosine, sphingomyelin, lactosylceramide, C18Cer (the naturally occurring ceramide), and dihydro C6Cer had no effect. A correlation was found between the ability of ceramides to inhibit bulk protein secretion and the inhibition of modeccin cytotoxicity by ceramides. Among Cer analogs tested, C6Cer, the most potent inhibitor of modeccin cytotoxicity, strongly inhibited bulk protein secretion in Vero, BER-40, and MDCK cells. PtK1 cells, which were not protected by ceramides against toxins, were resistant to ceramide-induced inhibition of bulk protein secretion. These results confirm that Cer may modulate the intracellular transport of proteins through the Golgi complex. Such Cer-sensitive processes may be involved in the intoxication of cells by plant and bacterial toxins, especially modeccin.

Animals↗
PubMed1995

Identification of cutC and cutF (nlpE) genes involved in copper tolerance in Escherichia coli.

It has been suggested previously that copper transport in Escherichia coli is mediated by the products of at least six genes, cutA, cutB, cutC, cutD, cutE, and cutF. A mutation in one or more of these genes results in an increased copper sensitivity (D. Rouch, J. Camakaris, and B. T. O. Lee, p. 469-477, in D. H. Hamer and D. R. Winge, ed., Metal Ion Homeostasis: Molecular Biology and Chemistry, 1989). Copper-sensitive cutC and cutF mutants were transformed with a genomic library of E. coli, and copper-tolerant transformants were selected. Two distinct clones were identified, each of which partially restores copper tolerance in both the cutC and cutF mutants of E. coli. Subcloning, physical mapping, and sequence analysis have revealed that the cutC gene is located at 42.15 min on the E. coli genome and encodes a cytoplasmic protein of 146 amino acids and that the cutF gene is located at 4.77 min on the E. coli genome and is allelic to the nlpE gene independently identified by Silhavy and coworkers (W. B. Snyder, L. J. B. Davis, P. N. Danese, C. L. Cosma, and T. J. Silhavy, J. Bacteriol. 177:4216-4223, 1995). Results from the genetic mapping of the copper-sensitive mutations in the cutF mutant and sequencing of the cutC and cutF (nlpE) alleles from both cutC and cutF mutants indicate that both the cutC and cutF mutants are in fact double mutants altered in these two genes, and mutations in both the genes appear to be required for the copper-sensitive phenotype in each mutant.

Alleles↗
PubMed1995

Structure-function relationship of bacterial prolipoprotein diacylglyceryl transferase: functionally significant conserved regions.

The structure-function relationship of bacterial prolipoprotein diacylgyceryl transferase (LGT) Has been investigated by a comparison of the primary structures of this enzyme in phylogenetically distant bacterial species, analysis of the sequences of mutant enzymes, and specific chemical modification of the Escherichia coli enzyme. A clone containing the gene for LGT, lgt, of the gram-positive species Staphylococcus aureus was isolated by complementation of the temperature-sensitive lgt mutant of E. coli (strain SK634) defective in LGT activity. In vivo and in vitro assays for prolipoprotein diacylglyceryl modification activity indicated that the complementing clone restored the prolipoprotein modification activity in the mutant strain. Sequence determination of the insert DNA revealed an open reading frame of 837 bp encoding a protein of 279 amino acids with a calculated molecular mass of 31.6 kDa. S. aureus LGT showed 24% identity and 47% similarity with E. coli, Salmonella typhimurium, and Haemophilus influenzae LGT.S. aureus LGT, while 12 amino acids shorter than the E. coli enzyme, had a hydropathic profile and a predicted pI (10.4) similar to those of the E. coli enzyme. Multiple sequence alignment among E. coli, S. typhimurium, H. influenzae, and S. aureus LGT proteins revealed regions of highly conserved amino acid sequences throughout the molecule. Three independent lgt mutant alleles from E. coli SK634, SK635, and SK636 and one lgt allele from S. typhimurium SE5221, all defective in LGT activity at the nonpermissive temperature, were cloned by PCR and sequenced. The mutant alleles were found to contain a single base alteration resulting in the substitution of a conserved amino acid. The longest set of identical amino acids without any gap was H-103-GGLIG-108 in LGT from these four microorganisms. In E. coli lgt mutant SK634, Gly-104 in this region was mutated to Ser, and the mutant organism was temperature sensitive in growth and exhibited low LGT activity in vitro. Diethylpyrocarbonate inactivated the E. coli LGT with a second-order rate constant of 18.6 M-1S-1, and the inactivation of LGT activity was reversed by hydroxylamine at pH 7. The inactivation kinetics were consistent with the modification of a single residue, His or Tyr, essential for LGT activity.

Amino Acid Sequence↗
PubMed1995

The umpA gene of Escherichia coli encodes phosphatidylglycerol:prolipoprotein diacylglyceryl transferase (lgt) and regulates thymidylate synthase levels through translational coupling.

Using a combination of biochemical, physical, and genetic techniques, we have shown that the umpA gene of Escherichia coli is allelic with the lgt (phosphatidylglycerol:prolipoprotein diacylglyceryl transferase) of Salmonella typhimurium. These genes are essential for the viability of the respective organism and exhibit 92.8% sequence identity at the amino acid level. In E. coli, lgt and thyA (thymidylate synthase) form an operon. Thymidylate synthase levels are regulated by transcription from the lgt promoter and by translational coupling.

Amino Acid Sequence↗
PubMed1995

Hepatopulmonary syndrome in liver cirrhosis: report of a case.

A 52-year-old woman suffered from exertional dyspnea, 5 years after she was diagnosed with cirrhosis of the liver. Hypoxemia was suspected because of persistent exertional dyspnea and was confirmed by contiguous arterial blood gas tests. After excluding other cardiopulmonary factors, a series of studies including lung perfusion scan, echocardiography and cardiopulmonary cineangiography revealed the cause of hypoxemia to be the patient's liver disease. Hepatopulmonary syndrome was diagnosed. Despite supplemental oxygen therapy and oral garlic powder for 6 months, the patient still had exertional dyspnea and platypnea, and arterial blood gas results did not improve. We report this case to call attention to arterial oxygen desaturation in cases of cirrhosis of the liver, and to emphasize that deteriorating oxygenation in patients with chronic liver disease may be an indication for liver transplantation, as such functional microvascular abnormalities could be reversed by liver transplantation.

Female↗
PubMed1994

Relationship of protein structure of isoleucyl-tRNA synthetase with pseudomonic acid resistance of Escherichia coli. A proposed mode of action of pseudomonic acid as an inhibitor of isoleucyl-tRNA synthetase.

To elucidate the mode of action of pseudomonic acid, we have compared the deduced amino acid sequences of isoleucyl-tRNA synthetases (ILeRS) from wild-type Escherichia coli strain MC4100, a pseudomonic acid-resistant mutant (strain PS102) of MC4100, and a pseudomonic acid-producing strain, Pseudomonas fluorescens. Compared with the wild-type enzyme, the deduced amino acid sequence of E. coli mutant ileS gene in strain PS102 shows a single amino acid substitution of leucine for phenylalanine at residue 594 of the IleRS. This mutational alteration in IleRS of an E. coli pseudomonic acid-resistant mutant resides in a region of the enzyme in close proximity to one of the consensus sequences of class I aminoacyl-tRNA synthetases, the KMSKS sequence between residues 602 and 606 of the E. coli IleRS. DNA sequence of the cloned ileS gene predicts that the P. fluorescens IleRS consists of 943 amino acids with 54% identity with the E. coli IleRS. The P. fluorescens ileS gene and the wild type and PS102 alleles of E. coli ileS were cloned into an expression vector, pEXPCR, and the sensitivities of E. coli DH5 alpha cells harboring each of these plasmids were compared. The cells harboring the P. fluorescens ileS were found to be most resistant to pseudomonic acid, while the transformants expressing the PS102 IleRS were more resistant than those containing the wild-type E. coli IleRS. IleRS purified from the wild-type E. coli was specifically cleaved by trypsin between Lys605 and Ser606 in the region of K602MSKS606. The protection of the IleRS from the trypsin digestion was found with pseudomonic acid or ATP, but not with isoleucine or tRNA(1Ile). Based on these results, we propose that pseudomonic acid binds to IleRS in the vicinity of the KMSKS sequence that is an ATP-binding subsite, and that pseudomonic acid is a bifunctional inhibitor with characteristics of both isoleucine and ATP, for example, an analog of isoleucyladenylate.

Adenosine Triphosphate↗
PubMed1994

Bowel perforation--a fatal complication following renal transplantation: a report of two cases.

From May 1983 to January 1993, 162 patients received renal transplantation at Taichung Veterans General Hospital. Two patients developed bowel perforation after this surgery. One was proved at 21 days and another, at 13 days after renal transplantation. Both patients died as a direct result of the perforation. From a review of literature, the average incidence is 2.7%, and the average mortality rate is 56.5%. Because of this high mortality rate, a high clinical suspicion, prompt and adequate surgical intervention, reduction of immunosuppressive agents and effective antibiotic coverage should contribute to a decline in mortality.

Adult↗
PubMed1993

Autocrine regulation of prostate-specific antigen gene expression in a human prostatic cancer (LNCaP) subline.

Prostate-specific antigen (PSA), a M(r) 34,000 serine protease, is recognized as a useful marker for the detection and prognosis of patients with prostate cancer. Although serum PSA is an excellent prognostic indicator, an increasing number of factors were found to regulate the PSA expression of prostatic cancer cells, which include androgenic steroids, the growth factors (GFs) and the extracellular matrix. The purpose of this study is to define a novel protein factor that may be responsible for regulating PSA expression by androgen-independent (AI) human prostate cancer cells. We have established a LNCaP subline (C4) from a parental LNCaP tumor grown in a castrated host. The C4 subline overexpressed PSA mRNA and protein. Serum-free conditioned medium (CM) isolated from the C4 subline is able to stimulate PSA gene expression in parental LNCaP cells in a concentration-dependent manner. This autocrine PSA-inducing activity was found to be organ specific because CMs from other fibroblast cell lines (such as bone, prostate, kidney, and lung fibroblasts) and the CMs from several prostatic carcinoma cell lines (such as parental LNCaP, PC-3, DU-145) and a bladder transitional carcinoma cell line (WH) fail to exhibit similar activity. The activity of the CM from the C4 subline cannot be substituted by GFs such as TGF-alpha, TGF-beta, bFGF, HGF, KGF, or NGF; neuropeptide (bombesin/GRP); secondary messenger analogue (dibutyryl cAMP); beta 2-adrenergic agonist (isoproterenol); or alpha 1-adrenergic agonist (phenylephrine), indicating that the factor(s) may be a novel prostate-specific autocrine factor (PSAF). Both androgen and PSAF exhibit an additive effect on up-regulating PSA gene expression, suggesting that the signal transduction pathway elicited by PSAF may differ from that mediated by the androgen receptor. Further characterization of PSAF by heat, acid, and trypsin digestion revealed that the PSAF may be a protein factor with a unique amino acid composition. These observations suggest that a novel autocrine pathway mediated by PSAF may be responsible for the overexpression of PSA mRNA and protein in a human prostatic cancer cell line. The potential clinical significance of this factor will be discussed.

Castration↗
PubMed1993

Characterization of seven newly established nasopharyngeal carcinoma cell lines.

BACKGROUND: Nasopharyngeal carcinoma (NPC) has a relatively high incidence in Chinese living in Taiwan, Hong Kong, Singapore, and South China. To better understand this cancer, we have established several new NPC cell lines. EXPERIMENTAL DESIGN: We collected biopsy specimens from suspected NPC patients and divided each specimen into two parts: the first part was fixed for routine histopathologic examination, and the other part was put into culture medium for primary culture. Once the cell lines were established, they were extensively characterized. RESULTS: Seven NPC cell lines were established, and all have been passaged more than 100 times. Two lines were derived from keratinizing carcinomas and five from undifferentiated carcinomas. Electron microscopic examination revealed that both dark and light tumor cells contained intermediate filaments with clear desmosome formation. The average doubling time ranged from 10.7 to 16.3 hours. Karyotypic analysis showed multiple chromosome abnormalities with the average chromosome number between 84 and 95. Colony forming efficiency in soft agar was 18-42%. All cell lines could induce solid tumor mass formation when transplanted into nude mice, and the histopathological findings showed two keratinizing and five nonkeratinizing carcinomas. All cell lines contained less acidic keratin polypeptides than basic keratin polypeptides. Strong expression of vimentin in each single cell of all cell lines was also observed. The oncosuppressor retinoblastoma gene in each cell line showed no remarkable abnormality, but retinoblastoma protein was abnormally expressed in some interphase cells. The oncogenes, erbB and c-fgr, were both normally expressed. While the c-myc oncogene in all cell lines was overexpressed when compared with the Burkitt's lymphoma Raji Cell line, the c-myc DNA sequence in each cell line showed neither amplification nor rearrangement. CONCLUSIONS: The newly established seven NPC cell lines have been well characterized, and all showed overexpression of c-myc oncogene. The oncosuppressor retinoblastoma gene revealed no remarkable rearrangement, but its protein product was abnormal in certain interphase cells of each cell line.

Adult↗
PubMed1992

Deletion of internal twenty-one amino acid residues of Escherichia coli prolipoprotein does not affect the formation of the murein-bound lipoprotein.

Mutation pgsA affecting the phosphatidylglycerol phosphate synthesis is lethal for all but certain E. coli strains such as strains deleted for the lpp gene or strains containing unmodifiable prolipoprotein like lppD14. Strain SD312 pgsA3 is tolerant to pgsA mutation, which suggests the lpp alleles in strain SD312 pgsA3 and its parental strain SD12 may be defective. DNA sequence analysis of the lpp genes in Escherichia coli strains SD12 and SD312 pgsA using asymmetric polymerase chain reaction showed that the lpp alleles in these two strains contained a 63 base pair deletion corresponding to the 37th to 57th codons of the wild-type lpp gene. [3H]Palmitate labeling of strains SD12 and SDS312 showed that the mutant lipoprotein in SD12 strain was modified with lipid, while the prolipoprotein in SD312 was not modified. The shortened mature lipoprotein in SD12 and the lipid-modified prolipoprotein in globomycin-treated SD12 were found to be covalently attached to the peptidoglycan, while the unmodified prolipoprotein in SD312 did not form significant amounts of murein-bound lipoprotein.

Alleles↗
PubMed1992

Staphylococcal ADP-ribosyltransferase-sensitive small G protein is involved in brefeldin A action.

An early event in the action of brefeldin A (BFA) is the dissociation of beta-coat protein (beta-COP) from the Golgi membrane. We have recently shown that staphylococcal ADP-ribosyltransferase (epidermal cell differentiation inhibitor (EDIN)), which specifically modifies a small G protein, rho, mimics the action of BFA and disassembles the Golgi apparatus in Vero cells (Sugai, M., Chen, C-h., and Wu, H. C. (1992) Proc. Natl. Acad. Sci. U.S.A. 89, 8903-8907). Three independent BFA-resistant cell lines (BER-40 from Vero cells, PtK1, and MDCK) showed cross-resistance to EDIN regarding the release of the beta-COP from the Golgi membrane by EDIN or BFA. BFA as well as EDIN induced disassembly of the actin microfilaments in Vero cells, and they both failed to induce the disassembly of actin microfilaments in BER-40, PtK1, and MDCK cells. BFA inhibited protein secretion in Vero cells but not in BFA-resistant cell lines, whereas EDIN did not inhibit protein secretion in either Vero or other cell lines. AlF-4 inhibited the effect of EDIN as well as that of BFA on the distribution of the beta-COP. These results suggest that an EDIN-sensitive rho protein together with trimeric and other small G protein(s) is involved in the regulation of the assembly of coated vesicles and vesicular transport in the Golgi apparatus.

Animals↗
PubMed1992

Bacterial ADP-ribosyltransferase with a substrate specificity of the rho protein disassembles the Golgi apparatus in Vero cells and mimics the action of brefeldin A.

Epidermal-cell differentiation inhibitor (EDIN) is an exoenzyme produced by Staphylococcus aureus that catalyzes the ADP-ribosylation of rho proteins, members of the small GTP-binding protein family. In this study we demonstrate that EDIN induces a rapid morphological change in the Golgi structure of monkey kidney Vero cells that is similar to the changes elicited by brefeldin A (BFA). Treatment of Vero cells with EDIN resulted in a rapid disappearance of N-7-(4-nitrobenzo-2-oxa-1,3-diazole)-6-aminocaproylsphingosine, a 110-kDa protein (beta-COP, coat protein), and mannosidase II from the Golgi structure. Lower doses of EDIN and BFA had a synergistic effect on the redistribution of the Golgi markers. The similarities in the effects of EDIN and BFA in Vero cells also include the EDIN- or BFA-mediated protection of Vero cells from ricin cytotoxicity and prevention of the effects of EDIN or BFA on the distribution of Golgi markers by the pretreatment of Vero cells with guanosine 5'-[gamma-thio]triphosphate or forskolin. Incubation of a Vero-cell homogenate with [32P]NAD+ and EDIN in vitro resulted in the appearance of a labeled band with an apparent molecular mass of 22 kDa. The morphological change of the Golgi structure induced by EDIN was inhibited by nicotinamide, an inhibitor of EDIN-catalyzed ADP-ribosylation. Thus these data suggest that a rho protein is involved in the membrane trafficking between the Golgi and the endoplasmic reticulum of Vero cells and that this rho protein may be a target shared by EDIN and BFA.

4-Chloro-7-nitrobenzofurazan↗
PubMed1992

Alterations of the carboxyl-terminal amino acid residues of Escherichia coli lipoprotein affect the formation of murein-bound lipoprotein.

Mutations in the Escherichia coli lpp gene resulting in the alterations of the COOH-terminal region of the lipoprotein have been isolated by oligonucleotide-directed mutagenesis. As might be expected, substitution of Lys78 with Arg78 completely abolished the formation of murein-bound lipoprotein. Each of the following single amino acid substitutions did not significantly affect the formation of bound-form lipoprotein: Asp70 to Glu70 or Gly70; Lys75 to Thr75; and Tyr76 to His76, Ile76, or Leu76. In contrast, mutational alterations of Tyr76 to Cys76, Gly76, Asn76, Pro76, or Ser76 resulted in a reduction of the bound-form lipoprotein to levels of 14-32% of that in the wild-type strain. A common feature of these lpp COOH-terminal mutations affecting the formation of bound-form lipoprotein is the presence of a beta-turn secondary structure at the COOH-terminal region of all these mutant lipoproteins. In addition, substitution of Tyr76 to Asp76 or Glu76, and Arg77 to Asp77 or Leu77 also resulted in a reduced formation of the bound-form lipoprotein. These results suggest that the formation of murein-bound lipoprotein requires a COOH-terminal Lys residue and a positively charged COOH-terminal region. Furthermore, a beta-turn secondary structure in the COOH-terminal random coil region interferes with the attachment of the lipoprotein to the peptidoglycan.

Amino Acid Sequence↗
PubMed1992

Neither lipid modification nor processing of prolipoprotein is essential for the formation of murein-bound lipoprotein in Escherichia coli.

The relationship between the modification and processing of prolipoprotein and the formation of murein-bound lipoprotein has been investigated using Escherichia coli mutants altered in the signal sequence of prolipoprotein and an E. coli strain producing OmpF-Lpp hybrid protein. The glyceride-modified prolipoprotein in mutant lppT20 and in globomycin-treated wild-type strain were covalently attached to the peptidoglycan. Likewise, the unmodified prolipoproteins in mutants lppL20, lppV20, and lppG21 were attached to the peptidoglycan. The OmpF-Lpp hybrid protein that is processed but not modified with lipid due to the absence of the cysteine-containing modification site in the hybrid protein was also covalently linked to the peptidoglycan. These results indicate that neither lipid modification nor the processing of prolipoprotein is essential for the formation of murein-bound lipoprotein in E. coli. In contrast, introduction of a charged amino acid residue such as Asp or Arg at the 14th position of prolipoprotein affected not only the lipid modification and processing of the mutant prolipoprotein but also the formation of murein-bound lipoprotein. Replacement of the Gly14 with Glu or Lys partially affected the lipid modification and processing of prolipoprotein; the peptidoglycan of the lppE14 and lppK14 mutants contained a reduced amount of mature lipoprotein but no mutant prolipoprotein. In addition, lpp mutants A20I23I24 and A20I23K24 were found to be defective in both lipid modification/processing of prolipoprotein and the formation of murein-bound lipoprotein. The defective formation of murein-bound lipoprotein in the latter mutants may be related to an alteration in the secondary structure at the modification/processing site of the mutant prolipoproteins.

Amino Acid Sequence↗