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Nguyen HT, Nguyen AH, Lam HM, Nguyen TT. Association of body mass index with non-achievement of target low-density lipoprotein level in older patients at very high cardiovascular risk: a multicentre study. Eur Heart J 2021. [DOI: 10.1093/eurheartj/ehab724.2801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Abstract
Introduction
Low-density lipoprotein cholesterol (LDL-c) is a well-established risk factor for atherosclerotic cardiovascular disease. Nonetheless, the association of body mass index (BMI) with non-achievement of target LDL-c level in older patients with type 2 diabetes (T2D) at very high cardiovascular risk is unknown.
Purpose
To investigate whether BMI is associated with non-achievement of target LDL-c level in older patients with T2D at very high cardiovascular risk.
Methods
From December 2019 to June 2020, in this multicentre prospective cross-sectional study, we enrolled 733 consecutive outpatients aged ≥60 years with T2D at very high cardiovascular risk in whom LDL-c levels could be measured after any stable lipid-lowering therapy for ≥6 months. Achievement of target lipid level was assessed based on the 2019 guidelines of the European Society of Cardiology for dyslipidaemia. Factors associated with non-achievement of target LDL-c level were determined using logistic regression analysis.
Results
Of the total cases (age, 68.6±7.2 years; men, 51.3%), 654 patients (89.2%) did not achieve an aggressive target LDL-c level of <1.4 mmol/L. Target non-high-density lipoprotein cholesterol level of <2.2 mmol/L and triglyceride level of <1.7 mmol/L were not achieved in 87.9% and 56.2% of the patients, respectively. In the multivariate model, BMI was the only factor associated with failure to achieve target LDL-c level, but not other factors such as age, sex, education level, smoking, and comorbidities. The adjusted odds ratio were 0.88 (95% confidence interval [95% CI], 0.24–3.21; P=0.84) for underweight, 1.57 (95% CI, 0.87–2.81; P=0.13) for overweight, and 2.63 (95% CI, 1.43–4.83; P=0.002) for obesity (normal weight was set as reference) status.
Conclusions
Non-achievement of target LDL-c level is highly prevalent in older patients with T2D at very high cardiovascular risk. Obesity, defined by BMI, can be a factor associated with non-achievement of the target. The findings highlight the importance of management of lipid levels in older patients with T2D.
Funding Acknowledgement
Type of funding sources: None. Figure 1
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Affiliation(s)
- H T Nguyen
- Ho Chi Minh City University of Medicine and Pharmacy, Geriatrics and Gerontology, Ho Chi Minh, Viet Nam
| | | | - H M Lam
- 175 Military Hospital, Ho Chi Minh, Viet Nam
| | - T T Nguyen
- Thong Nhat Hospital, CARDIOLOGY, Ho Chi Minh, Viet Nam
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Chan CY, Zheng XD, Chan LY, Cui H, Ginn EWL, Leung YK, Lam HM, Zheng YG, Qin Y, Zhao CS, Wang T, Blake DR, Li YS. Vertical profile and origin of wintertime tropospheric ozone over China during the PEACE-A period. ACTA ACUST UNITED AC 2004. [DOI: 10.1029/2004jd004581] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- C. Y. Chan
- Department of Civil and Structural Engineering; Hong Kong Polytechnic University; Hong Kong China
| | - X. D. Zheng
- Chinese Academy of Meteorological Sciences; Beijing China
| | - L. Y. Chan
- Department of Civil and Structural Engineering; Hong Kong Polytechnic University; Hong Kong China
| | - H. Cui
- Department of Civil and Structural Engineering; Hong Kong Polytechnic University; Hong Kong China
| | | | | | - H. M. Lam
- Department of Civil and Structural Engineering; Hong Kong Polytechnic University; Hong Kong China
| | - Y. G. Zheng
- Department of Atmospheric Sciences; Peking University; Beijing China
| | - Y. Qin
- Department of Atmospheric Sciences; Peking University; Beijing China
| | - C. S. Zhao
- Department of Atmospheric Sciences; Peking University; Beijing China
| | - T. Wang
- Department of Civil and Structural Engineering; Hong Kong Polytechnic University; Hong Kong China
| | - D. R. Blake
- Department of Chemistry; University of California; Irvine California USA
| | - Y. S. Li
- Department of Civil and Structural Engineering; Hong Kong Polytechnic University; Hong Kong China
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O'Driscoll J, Muston GC, McGrath JA, Lam HM, Ashworth J, Christiano AM. A recurrent mutation in the loricrin gene underlies the ichthyotic variant of Vohwinkel syndrome. Clin Exp Dermatol 2002; 27:243-6. [PMID: 12072018 DOI: 10.1046/j.1365-2230.2002.01031.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Vohwinkel syndrome (VS) is a family of genodermatoses which exhibits extensive clinical and genetic heterogeneity. Here, we studied a pedigree originating from the UK with typical features of the ichthyotic variant of VS and identified a recurrent insertion mutation in the loricrin gene resulting in a mutant polypeptide with an unusual C terminus. Functional studies in transgenic mice have shown that the accumulation of mutant loricrin in the nucleus appears to interfere with the later stages of epidermal differentiation, thereby explaining the clinical manifestations of ichthyosis, keratoderma and pseudoainhum. Our findings extend the body of evidence implicating mutations in the loricrin gene as the underlying cause of VS.
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Lam HM. [Not Available]. Abh Gesch Med Naturwiss 2001:1990;57, 59-68. [PMID: 11678127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
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Oliveira IC, Brenner E, Chiu J, Hsieh MH, Kouranov A, Lam HM, Shin MJ, Coruzzi G. Metabolite and light regulation of metabolism in plants: lessons from the study of a single biochemical pathway. Braz J Med Biol Res 2001; 34:567-75. [PMID: 11323742 DOI: 10.1590/s0100-879x2001000500003] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We are using molecular, biochemical, and genetic approaches to study the structural and regulatory genes controlling the assimilation of inorganic nitrogen into the amino acids glutamine, glutamate, aspartate and asparagine. These amino acids serve as the principal nitrogen-transport amino acids in most crop and higher plants including Arabidopsis thaliana. We have begun to investigate the regulatory mechanisms controlling nitrogen assimilation into these amino acids in plants using molecular and genetic approaches in Arabidopsis. The synthesis of the amide amino acids glutamine and asparagine is subject to tight regulation in response to environmental factors such as light and to metabolic factors such as sucrose and amino acids. For instance, light induces the expression of glutamine synthetase (GLN2) and represses expression of asparagine synthetase (ASN1) genes. This reciprocal regulation of GLN2 and ASN1 genes by light is reflected at the level of transcription and at the level of glutamine and asparagine biosynthesis. Moreover, we have shown that the regulation of these genes is also reciprocally controlled by both organic nitrogen and carbon metabolites. We have recently used a reverse genetic approach to study putative components of such metabolic sensing mechanisms in plants that may be conserved in evolution. These components include an Arabidopsis homolog for a glutamate receptor gene originally found in animal systems and a plant PII gene, which is a homolog of a component of the bacterial Ntr system. Based on our observations on the biology of both structural and regulatory genes of the nitrogen assimilatory pathway, we have developed a model for metabolic control of the genes involved in the nitrogen assimilatory pathway in plants.
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Affiliation(s)
- I C Oliveira
- Department of Biology, New York University, New York, NY 10003, USA
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Lam HM. [From an urge for life to a wish to die. A sociocultural analysis]. Tijdschr Gerontol Geriatr 1999; 30:109-13. [PMID: 10422206] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/13/2023]
Abstract
In euthanasia and assisted suicide the wish to die has become greater than the wish to continue life. The reasons of this turn to death are subject of analysis. Examples, two from the Netherlands and one from the Eskimos demonstrate that the beginning of this process is an experience of irreversible loss. Cultural norms determine the meaning of this experience. Likewise, prevailing norms determine the possible unacceptability of the resulting deviancy. Coping with unacceptable deviancy is a restaurative strategy which fits in the prevailing cultural model. Eskimo assisted suicide is aimed at sectional interest: the request for life-ending help is posed on behalf of group survival. In the Netherlands euthanasia and assisted suicide are part of an individualistic culture with an earthly system of meaning. The emphasis is on good health, youth and representative appearance. The individual request for help is posed on behalf of the individual himself, to prevent social isolation, and to die in a clean way in self-selected company.
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Chiu J, DeSalle R, Lam HM, Meisel L, Coruzzi G. Molecular evolution of glutamate receptors: a primitive signaling mechanism that existed before plants and animals diverged. Mol Biol Evol 1999; 16:826-38. [PMID: 10368960 DOI: 10.1093/oxfordjournals.molbev.a026167] [Citation(s) in RCA: 140] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We performed a genealogical analysis of the ionotropic glutamate receptor (iGluR) gene family, which includes the animal iGluRs and the newly isolated glutamate receptor-like genes (GLR) of plants discovered in Arabidopsis. Distance measures firmly placed the plant GLR genes within the iGluR clade as opposed to other ion channel clades and indicated that iGluRs may be a primitive signaling mechanism that predated the divergence of animals and plants. Moreover, phylogenetic analyses using both parsimony and neighbor joining indicated that the divergence of animal iGluRs and plant GLR genes predated the divergence of iGluR subtypes (NMDA vs. AMPA/KA) in animals. By estimating the congruence of the various glutamate receptor gene regions, we showed that the different functional domains, including the two ligand-binding domains and the transmembrane regions, have coevolved, suggesting that they assembled together before plants and animals diverged. Based on residue conservation and divergence as well as positions of residues with respect to functional domains of iGluR proteins, we attempted to examine structure-function relationships. This analysis defined M3 as the most highly conserved transmembrane domain and identified potential functionally important conserved residues whose function can be examined in future studies.
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Affiliation(s)
- J Chiu
- Department of Biology, New York University, New York 10003, USA
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Abstract
Lamellar ichthyosis (LI) is an autosomal recessive disorder of cornification. Mutations in the transglutaminase 1 gene (TGM1) have been identified in several families with this disorder. We analyzed two unrelated families with offspring affected with LI. Family 1 included affected monozygotic twins, in which a homozygous G-to-T transversion was identified in exon 6 at amino acid residue R315L. This mutation was also identified in the unaffected mother. In family 2, which consisted of one affected infant, a T-to-G transversion in exon 8 resulted in a change of phenylalanine to valine, F400V, and a C-to-T transition in exon 4 resulted in a change of proline to leucine, P248L. In this family, the mutation F400V was found in the unaffected father, and the mutation P248L was identified in the unaffected mother. These findings extend the growing body of literature documenting mutations in the TGM1 gene as the molecular basis of certain cases of lamellar ichthyosis.
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Affiliation(s)
- J Tok
- Department of Dermatology, Columbia University, College of Physicians & Surgeons, New York, NY 10032, USA
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Hsieh MH, Lam HM, van de Loo FJ, Coruzzi G. A PII-like protein in Arabidopsis: putative role in nitrogen sensing. Proc Natl Acad Sci U S A 1998; 95:13965-70. [PMID: 9811909 PMCID: PMC24990 DOI: 10.1073/pnas.95.23.13965] [Citation(s) in RCA: 167] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/1998] [Indexed: 11/18/2022] Open
Abstract
PII is a protein allosteric effector in Escherichia coli and other bacteria that indirectly regulates glutamine synthetase at the transcriptional and post-translational levels in response to nitrogen availability. Data supporting the notion that plants have a nitrogen regulatory system(s) includes previous studies showing that the levels of mRNA for plant nitrogen assimilatory genes such as glutamine synthetase (GLN) and asparagine synthetase (ASN) are modulated by carbon and organic nitrogen metabolites. Here, we have characterized a PII homolog (GLB1) in two higher plants, Arabidopsis thaliana and Ricinus communis (Castor bean). Each plant PII-like protein has high overall identity to E. coli PII (50%). Western blot analyses reveal that the plant PII-like protein is a nuclear-encoded chloroplast protein. The PII-like protein of plants appears to be regulated at the transcriptional level in that levels of GLB1 mRNA are affected by light and metabolites. To initiate studies of the in vivo function of the Arabidopsis PII-like protein, we have constructed transgenic lines in which PII expression is uncoupled from its native regulation. Analyses of these transgenic plants support the notion that the plant PII-like protein may serve as part of a complex signal transduction network involved in perceiving the status of carbon and organic nitrogen. Thus, the PII protein found in archaea, bacteria, and now in higher eukaryotes (plants) is one of the most widespread regulatory proteins known, providing evidence for an ancestral metabolic regulatory mechanism that may have existed before the divergence of these three domains of life.
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Affiliation(s)
- M H Hsieh
- Department of Biology, New York University, New York, NY 10003, USA
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Abstract
In plants, the amino acid asparagine serves as an important nitrogen transport compound whose levels are dramatically regulated by light in many plant species, including Arabidopsis thaliana. To elucidate the mechanisms regulating the flux of assimilated nitrogen into asparagine, we examined the regulation of the gene family for asparagine synthetase in Arabidopsis. In addition to the previously identified ASN1 gene, we identified a novel class of asparagine synthetase genes in Arabidopsis (ASN2 and ASN3) by functional complementation of a yeast asparagine auxotroph. The proteins encoded by the ASN2/3 cDNAs contain a Pur-F type glutamine-binding triad suggesting that they, like ASN1, encode glutamine-dependent asparagine synthetase isoenzymes. However, the ASN2/3 isoenzymes form a novel dendritic group with monocot AS genes which is distinct from all other dicot AS genes including Arabidopsis ASN1. In addition to these distinctions in sequence, the ASN1 and ASN2 genes are reciprocally regulated by light and metabolites. Time-course experiments reveal that light induces levels of ASN2 mRNA while it represses levels of ASN1 mRNA in a kinetically reciprocal fashion. Moreover, the levels of ASN2 and ASN1 mRNA are also reciprocally regulated by carbon and nitrogen metabolites. The distinct regulation of ASN1 and ASN2 genes combined with their distinct encoded isoenzymes suggest that they may play different roles in nitrogen metabolism, as discussed in this paper.
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Affiliation(s)
- H M Lam
- Chinese University of Hong Kong, Department of Biology, Shantin, N.T
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Frank J, Wang X, Lam HM, Aita VM, Jugert FK, Goerz G, Merk HF, Poh-Fitzpatrick MB, Christiano AM. C73R is a hotspot mutation in the uroporphyrinogen III synthase gene in congenital erythropoietic porphyria. Ann Hum Genet 1998; 62:225-30. [PMID: 9803266 DOI: 10.1046/j.1469-1809.1998.6230225.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Congenital erythropoietic porphyria (CEP) results from profoundly deficient activity of the fourth enzyme of the haeme biosynthetic pathway, uroporphyrinogen III synthase (UROIIIS). CEP is a rare, recessively inherited disorder, and mutations in the UROIIIS gene detected in CEP patients are heterogeneous. The notable exception to this rule is a single missense mutation, designated C73R, which represents over 40% of all mutant UROIIIS alleles. In this study, we investigated three separate families with CEP from different ethnic backgrounds. We performed haplotype analysis using two microsatellite markers that closely flank the UROIIIS gene on chromosome 10q24, spanning a region of 4 cM on the GB4 linkage panel. Haplotype analysis revealed the occurrence of C73R on different haplotypes in four out of four disease chromosomes studied. The results are consistent with the hypothesis that C73R is a hotspot mutation for CEP, and does not represent wide dispersion of a single ancestral mutant C73R allele.
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Affiliation(s)
- J Frank
- Department of Dermatology, Columbia University, College of Physicians and Surgeons, New York, NY 10032, USA
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Lam HM, Coschigano K, Schultz C, Melo-Oliveira R, Tjaden G, Oliveira I, Ngai N, Hsieh MH, Coruzzi G. Use of Arabidopsis mutants and genes to study amide amino acid biosynthesis. Plant Cell 1995; 7:887-98. [PMID: 7640525 PMCID: PMC160882 DOI: 10.1105/tpc.7.7.887] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Affiliation(s)
- H M Lam
- Department of Biology, New York University, New York 10003, USA
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Lam HM, Peng SS, Coruzzi GM. Metabolic regulation of the gene encoding glutamine-dependent asparagine synthetase in Arabidopsis thaliana. Plant Physiol 1994; 106:1347-57. [PMID: 7846154 PMCID: PMC159672 DOI: 10.1104/pp.106.4.1347] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Here, we characterize a cDNA encoding a glutamine-dependent asparagine synthetase (ASN1) from Arabidopsis thaliana and assess the effects of metabolic regulation on ASN1 mRNA levels. Sequence analysis shows that the predicted ASN1 peptide contains a purF-type glutamine-binding domain. Southern blot experiments and cDNA clone analysis suggest that ASN1 is the only gene encoding glutamine-dependent asparagine synthetase in A. thaliana. The ASN1 gene is expressed predominantly in shoot tissues, where light has a negative effect on its mRNA accumulation. This negative effect of light on ASN1 mRNA levels was shown to be mediated, at least in part, via the photoreceptor phytochrome. We also investigated whether light-induced changes in nitrogen to carbon ratios might exert a metabolic regulation of the ASN1 mRNA accumulation. These experiments demonstrated that the accumulation of ASN1 mRNA in dark-grown plants is strongly repressed by the presence of exogenous sucrose. Moreover, this sucrose repression of ASN1 expression can be partially rescued by supplementation with exogenous amino acids such as asparagine, glutamine, and glutamate. These findings suggest that the expression of the ASN1 gene is under the metabolic control of the nitrogen to carbon ratio in cells. This is consistent with the fact that asparagine, synthesized by the ASN1 gene product, is a favored compound for nitrogen storage and nitrogen transport in dark-grown plants. We have put forth a working model suggesting that when nitrogen to carbon ratios are high, the gene product of ASN1 functions to re-direct the flow of nitrogen into asparagine, which acts as a shunt for storage and/or long-distance transport of nitrogen.
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Affiliation(s)
- H M Lam
- Department of Biology, New York University, New York 10003
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Lam HM, Winkler ME. Characterization of the complex pdxH-tyrS operon of Escherichia coli K-12 and pleiotropic phenotypes caused by pdxH insertion mutations. J Bacteriol 1992; 174:6033-45. [PMID: 1356963 PMCID: PMC207668 DOI: 10.1128/jb.174.19.6033-6045.1992] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We report the first molecular genetic analysis of a pyridoxine 5'-phosphate oxidase, the PdxH gene product of Escherichia coli K-12. Chromosomal insertions in and around pdxH were generated with various transposons, and the resulting phenotypes were characterized. The DNA sequence of pdxH was determined, and the promoters of pdxH and the downstream gene tyrS, which encodes tyrosyl-tRNA synthetase, were mapped by RNase T2 protection assays of chromosomal transcripts. These combined approaches led to the following conclusions: (i) pdxH is transcribed from a sigma 70-type promoter and shares its transcript with tyrS; (ii) tyrS is additionally transcribed from a relatively strong, nonconventional internal promoter that may contain an upstream activating sequence but whose expression is unaffected by a fis mutation; (iii) PdxH oxidase is basic, has a molecular mass of 25,545 Da, and shares striking homology (greater than 40% identity) with the developmentally regulated FprA protein of Myxococcus xanthus; (iv) mild pyridoxal 5'-phosphate limitation of pdxH mutants inhibits cell division and leads to formation of unsegregated nucleoids; (v) E. coli PdxH oxidase is required aerobically and anaerobically, but second-site suppressors that replace pdxH function entirely can be isolated; and (vi) pdxH mutants excrete significant amounts of L-glutamate and a compound, probably alpha-ketoisovalerate, that triggers L-valine inhibition of E. coli K-12 strains. These findings extend earlier observations that pyridoxal 5'-phosphate biosynthetic and aminoacyl-tRNA synthetase genes are often members of complex, multifunctional operons. Our results also show that loss of pdxH function seriously disrupts cellular metabolism in unanticipated ways.
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Affiliation(s)
- H M Lam
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston 77030
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Abstract
Complementation analyses using minimal recombinant clones showed that all known pdx point mutations, which cause pyridoxine (vitamin B6) or pyridoxal auxotrophy, are located in the pdxA, pdxB, serC, pdxJ, and pdxH genes. Antibiotic enrichments for chromosomal transposon mutants that require pyridoxine (vitamin B6) or pyridoxal led to the isolation of insertions in pdxA, pdxB, and pdxH but not in pdxJ. This observation suggested that pdxJ, like pdxA, pdxB, and serC, might be in a complex operon. To test this hypothesis, we constructed stable insertion mutations in and around pdxJ in plasmids and forced them into the bacterial chromosome. Physiological properties of the resulting insertion mutants were characterized, and the DNA sequence of pdxJ and adjacent regions was determined. These combined approaches led to the following conclusions: (i) pdxJ is the first gene in a two-gene operon that contains a gene, temporarily designated dpj, essential for Escherichia coli growth; (ii) expression of the rnc-era-recO and pdxJ-dpj operons can occur independently, although the pdxJ-dpj promoter may lie within recO; (iii) pdxJ encodes a 26,384-Da polypeptide whose coding region is preceded by a PDX box, and dpj probably encodes a basic, 14,052-Da polypeptide; (iv) mini-Mud insertions in dpj and pdxJ, which are polar on dpj, severely limit E. coli growth; and (v) three classes of suppressors, including mutations in lon and suppressors of lon, that allow faster growth of pdxJ::mini-Mud mutants can be isolated. A model to account for the action of dpj suppressors is presented, and aspects of this genetic analysis are related to the pyridoxal 5'-phosphate biosynthetic pathway.
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Affiliation(s)
- H M Lam
- Department of Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611
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Abstract
We propose a pathway leading from erythrose-4-phosphate and glutamate to nitrogen 1 and carbons 5,5', and 6 of the pyridoxine ring. This pathway, which parallels the phosphorylated pathway of serine biosynthesis, is predicted on the homology between PdxB and SerA, the structural similarity between serine and 4-hydroxythreonine, and the possible involvement of SerC in pyridoxine biosynthesis. Several predictions of this hypothetical scheme were tested. Consistent with the proposed pathway, supplement inhibition patterns strongly suggest that SerA enzyme acts in a an alternate pathway of pyridoxine biosynthesis in pdxB mutants. Direct enzyme assays detected erythrose-4-phosphate dehydrogenase activity in crude extracts, which again supports the proposed pathway. Chromosomal insertions in serC caused a requirement for pyridoxine, serine, and aromatic compounds, which directly verified that SerC functions in the pyridoxine biosynthetic pathway. Complementation analysis showed that pdxF and pdxC mutations reported previously are most likely alleles of serC. Growth of serC chromosomal insertion mutants on glycoalaldehyde was found to occur without acquisition of second-site mutations and confirmed that pdxB and serC, but not pdxA, function in the same branch of the pyridoxine pathway. In addition, serC::mini-Mu d insertions revealed that the complex serC-aroA operon lacks internal promoters, that the amino terminus of SerC is not strictly essential for activity, and that antisense transcription occurs in the serC-aroA operon. Growth responses of pdxA, pdxB, and serC mutants to beta-hydroxypyruvate, D-alanine, and glycolate could also be reconciled with the proposed pathway. Finally, the proposed scheme is consistent with previous isotope labeling data and accounts for several other observations about pyridoxine biosynthesis. Together, these physiological and biochemical analyses support the proposed pathway and an evolutionary scenario in which this branch of the pyridoxine pathway evolved from the serine pathway by gene recruitment.
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Affiliation(s)
- H M Lam
- Department of Molecular Biology, Northwestern University Medical School, Chicago, Illinois 60611
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van der Zel A, Lam HM, Winkler ME. Extensive homology between the Escherichia coli K-12 SerC(PdxF) aminotransferase and a protein encoded by a progesterone-induced mRNA in rabbit and human endometria. Nucleic Acids Res 1989; 17:8379. [PMID: 2682527 PMCID: PMC334985 DOI: 10.1093/nar/17.20.8379] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Affiliation(s)
- A van der Zel
- Department of Molecular Biology, Northwestern University Medical School, Chicago, IL 60611
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Abstract
1. The anatomy of the counter-current heat exchanger of skipjack tuna is described and the pattern of blood flow is analysed.
2. The pattern of blood flow is from the dorsal aorta, through the exchanger to segmental arteries to the tissues, from the tissues to segmental veins and back through the exchanger to the post-cardinal vein.
3. The vessels in the exchanger are about the same size as systemic arterioles and venules and are about 10 mm long. There are about 125000 of each type in a 2 kg tuna.
4. The velocity of blood flow in the exchanger is about 1/80th of that in the dorsal aorta and post-cardinal vein allowing time for heat transfer.
5. There are many valves in the segmental veins which may be expected because of the resistance offered by the exchanger.
6. The vessels in the tuna heat exchanger are an order of magnitude larger than those in the swim-bladder rete, thus permitting heat transfer but preventing gas transfer.
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