26
|
Johnson TW, Richardson PF, Bailey S, Brooun A, Burke BJ, Collins MR, Cui JJ, Deal JG, Deng YL, Dinh D, Engstrom LD, He M, Hoffman J, Hoffman RL, Huang Q, Kania RS, Kath JC, Lam H, Lam JL, Le PT, Lingardo L, Liu W, McTigue M, Palmer CL, Sach NW, Smeal T, Smith GL, Stewart AE, Timofeevski S, Zhu H, Zhu J, Zou HY, Edwards MP. Discovery of (10R)-7-Amino-12-fluoro-2,10,16-trimethyl-15-oxo-10,15,16,17-tetrahydro-2H-8,4-(metheno)pyrazolo[4,3-h][2,5,11]-benzoxadiazacyclotetradecine-3-carbonitrile (PF-06463922), a Macrocyclic Inhibitor of Anaplastic Lymphoma Kinase (ALK) and c-ros Oncogene 1 (ROS1) with Preclinical Brain Exposure and Broad-Spectrum Potency against ALK-Resistant Mutations. J Med Chem 2014; 57:4720-44. [DOI: 10.1021/jm500261q] [Citation(s) in RCA: 350] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
|
27
|
Huang Q, Johnson TW, Bailey S, Brooun A, Bunker KD, Burke BJ, Collins MR, Cook AS, Cui JJ, Dack KN, Deal JG, Deng YL, Dinh D, Engstrom LD, He M, Hoffman J, Hoffman RL, Johnson PS, Kania RS, Lam H, Lam JL, Le PT, Li Q, Lingardo L, Liu W, Lu MW, McTigue M, Palmer CL, Richardson PF, Sach NW, Shen H, Smeal T, Smith GL, Stewart AE, Timofeevski S, Tsaparikos K, Wang H, Zhu H, Zhu J, Zou HY, Edwards MP. Design of Potent and Selective Inhibitors to Overcome Clinical Anaplastic Lymphoma Kinase Mutations Resistant to Crizotinib. J Med Chem 2014; 57:1170-87. [DOI: 10.1021/jm401805h] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
|
28
|
Johnson TW, Bailey S, Burke BJ, Collins MR, Cui JJ, Deal J, Deng YL, Edwards MP, He M, Hoffman J, Hoffman RL, Huang Q, Kania RS, Le P, McTigue M, Palmer CL, Richardson PF, Sach NW, Smith GL, Engstrom L, Hu W, Lam H, Lam JL, Smeal T, Zou HY. Abstract PR10: Is CNS availability for oncology a no-brainer? Discovery of PF-06463922, a novel small molecule inhibitor of ALK/ROS1 with preclinical brain availability and broad spectrum potency against ALK-resistant mutations. Mol Cancer Ther 2013. [DOI: 10.1158/1535-7163.targ-13-pr10] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Abstract
Oncogenic fusions of anaplastic lymphoma kinase (ALK) define a subset of human lung adenocarcinoma. The 1st generation ALK inhibitor crizotinib demonstrated impressive clinical benefit in ALK-fusion positive lung cancers and was approved by the FDA for the treatment of ALK-fusion positive NSCLC in 2011. However, as seen with most kinase inhibitors, patients treated with crizotinib eventually develop resistance to therapy. Acquired ALK kinase domain mutations and disease progression in the central nervous system (CNS) are reported as main contributors to patient relapse after ALK inhibitor therapy. Preclinically, crizotinib lacks significant brain penetration and does not potently inhibit activity of ALK kinase domain mutants, so a drug discovery program was initiated aimed to develop a second generation ALK inhibitor that is more potent than existing ALK inhibitors, capable of inhibiting the resistant ALK mutants and penetrating the blood-brain-barrier. These objectives present a considerable challenge in kinase inhibitor chemical space. Here we report that PF-06463922, a novel small molecule ATP-competitive inhibitor of ALK/ROS1, showed exquisite potencies against non-mutant ALK (Ki <0.2 nM; cell IC50 ∼2 nM) and ROS1 kinase (Ki <0.005 nM; cell IC50 ∼0.2 nM), and demonstrated low nanomolar inhibitory activity against a panel of ALK kinase domain mutants representing all of the patient crizotinib resistant mutations reported to date. The more commonly reported L1196M gatekeeper mutant shows significant sensitivity to PF-06463922 (Ki 0.7 nM; cell IC50 16 nM). PF-06463922 is also very selective, and showed >100 fold kinase selectivity against 95% of the kinases tested in a 207 recombinant kinase panel. Specific design considerations were developed leading to novel ATP-competitive kinase inhibitors with desired low efflux in cell lines over-expressing p-glycoprotein and breast cancer resistance protein, providing excellent blood-brain-barrier and cell penetration properties. Efforts to optimize ligand efficiency and lipophilic efficiency leveraging structure based drug design techniques led to ligands with overlapping broad spectrum potency and low efflux. Single and repeat dose preclinical rat in vivo studies of PF-06463922 demonstrated excellent oral bioavailability and CNS availability with free brain exposure approximately 30% of free plasma levels. In addition, CNS-directed safety studies showed no adverse events at predicted efficacious concentrations. It is anticipated that PF-06463922 with its potent activities on non-mutant ALK, ALK kinase domain mutations and CNS metastases would provide great promise for patients with ALK and ROS1 positive cancers.
Citation Information: Mol Cancer Ther 2013;12(11 Suppl):PR10.
Citation Format: Ted W. Johnson, Simon Bailey, Benjamin J. Burke, Michael R. Collins, J. Jean Cui, Judy Deal, Ya-Li Deng, Martin P. Edwards, Mingying He, Jacqui Hoffman, Robert L. Hoffman, Qinhua Huang, Robert S. Kania, Phuong Le, Michele McTigue, Cynthia L. Palmer, Paul F. Richardson, Neal W. Sach, Graham L. Smith, Lars Engstrom, Wenyue Hu, Hieu Lam, Justine L. Lam, Tod Smeal, Helen Y. Zou. Is CNS availability for oncology a no-brainer? Discovery of PF-06463922, a novel small molecule inhibitor of ALK/ROS1 with preclinical brain availability and broad spectrum potency against ALK-resistant mutations. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr PR10.
Collapse
|
29
|
Cheng H, Li C, Bailey S, Baxi SM, Goulet L, Guo L, Hoffman J, Jiang Y, Johnson TO, Johnson TW, Knighton DR, Li J, Liu KKC, Liu Z, Marx MA, Walls M, Wells PA, Yin MJ, Zhu J, Zientek M. Discovery of the Highly Potent PI3K/mTOR Dual Inhibitor PF-04979064 through Structure-Based Drug Design. ACS Med Chem Lett 2013; 4:91-7. [PMID: 24900568 DOI: 10.1021/ml300309h] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2012] [Accepted: 11/07/2012] [Indexed: 11/30/2022] Open
Abstract
PI3K, AKT, and mTOR are key kinases from PI3K signaling pathway being extensively pursued to treat a variety of cancers in oncology. To search for a structurally differentiated back-up candidate to PF-04691502, which is currently in phase I/II clinical trials for treating solid tumors, a lead optimization effort was carried out with a tricyclic imidazo[1,5]naphthyridine series. Integration of structure-based drug design and physical properties-based optimization yielded a potent and selective PI3K/mTOR dual kinase inhibitor PF-04979064. This manuscript discusses the lead optimization for the tricyclic series, which both improved the in vitro potency and addressed a number of ADMET issues including high metabolic clearance mediated by both P450 and aldehyde oxidase (AO), poor permeability, and poor solubility. An empirical scaling tool was developed to predict human clearance from in vitro human liver S9 assay data for tricyclic derivatives that were AO substrates.
Collapse
|
30
|
Johnson TW, White S, Gnanadesigan M, Bourenane H, Strange JW, Newby AC, van Soest G, Baumbach A. 023 An ex-vivo “whole human heart model” for the development of intravascular imaging. BRITISH HEART JOURNAL 2012. [DOI: 10.1136/heartjnl-2012-301877b.23] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
|
31
|
Johnson TW, Strange JW, Oriolo V, Edmond J, Davies A, Reeves BC, Baumbach A. 132 Combined prasugrel and bivalirudin treatment during primary PCI offers a safe and effective strategy in ST-elevation MI. BRITISH HEART JOURNAL 2012. [DOI: 10.1136/heartjnl-2012-301877b.132] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
|
32
|
Johnson TW, Tanis SP, Butler SL, Dalvie D, Delisle DM, Dress KR, Flahive EJ, Hu Q, Kuehler JE, Kuki A, Liu W, McClellan GA, Peng Q, Plewe MB, Richardson PF, Smith GL, Solowiej J, Tran KT, Wang H, Yu X, Zhang J, Zhu H. Design and synthesis of novel N-hydroxy-dihydronaphthyridinones as potent and orally bioavailable HIV-1 integrase inhibitors. J Med Chem 2011; 54:3393-417. [PMID: 21446745 DOI: 10.1021/jm200208d] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
HIV-1 integrase (IN) is one of three enzymes encoded by the HIV genome and is essential for viral replication, and HIV-1 IN inhibitors have emerged as a new promising class of therapeutics. Recently, we reported the synthesis of orally bioavailable azaindole hydroxamic acids that were potent inhibitors of the HIV-1 IN enzyme. Here we disclose the design and synthesis of novel tricyclic N-hydroxy-dihydronaphthyridinones as potent, orally bioavailable HIV-1 integrase inhibitors displaying excellent ligand and lipophilic efficiencies.
Collapse
|
33
|
Tanis SP, Plewe MB, Johnson TW, Butler SL, Dalvie D, DeLisle D, Dress KR, Hu Q, Huang B, Kuehler JE, Kuki A, Liu W, Peng Q, Smith GL, Solowiej J, Tran KT, Wang H, Yang A, Yin C, Yu X, Zhang J, Zhu H. Azaindole N-methyl hydroxamic acids as HIV-1 integrase inhibitors-II. The impact of physicochemical properties on ADME and PK. Bioorg Med Chem Lett 2010; 20:7429-34. [DOI: 10.1016/j.bmcl.2010.10.022] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2010] [Revised: 10/02/2010] [Accepted: 10/05/2010] [Indexed: 11/24/2022]
|
34
|
Plewe MB, Butler SL, R. Dress K, Hu Q, Johnson TW, Kuehler JE, Kuki A, Lam H, Liu W, Nowlin D, Peng Q, Rahavendran SV, Tanis SP, Tran KT, Wang H, Yang A, Zhang J. Azaindole Hydroxamic Acids are Potent HIV-1 Integrase Inhibitors. J Med Chem 2009; 52:7211-9. [DOI: 10.1021/jm900862n] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
35
|
Johnson TW, Dress KR, Edwards M. Using the Golden Triangle to optimize clearance and oral absorption. Bioorg Med Chem Lett 2009; 19:5560-4. [PMID: 19720530 DOI: 10.1016/j.bmcl.2009.08.045] [Citation(s) in RCA: 196] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Revised: 08/10/2009] [Accepted: 08/12/2009] [Indexed: 10/20/2022]
Abstract
The Golden Triangle is a visualization tool developed from in vitro permeability, in vitro clearance and computational data designed to aid medicinal chemists in achieving metabolically stable, permeable and potent drug candidates. Classifying compounds as permeable and stable and plotting molecular weight (MW) versus octanol:buffer (pH 7.4) distribution coefficients (logD) or estimated octanol:buffer (pH 7.4) distribution coefficients (elogD) reveals useful trends. Analysis of at least two orthogonal trends, such as permeability and clearance, can be extremely effective in balancing and optimizing multiple properties. In addition, molecular weight and logD impact potency-efficiency calculations, allowing potency, clearance and permeability to be optimized simultaneously.
Collapse
|
36
|
Rasmussen LS, O'Brien JT, Silverstein JH, Johnson TW, Siersma VD, Canet J, Jolles J, Hanning CD, Kuipers HM, Abildstrom H, Papaioannou A, Raeder J, Yli-Hankala A, Sneyd JR, Munoz L, Moller JT. Is peri-operative cortisol secretion related to post-operative cognitive dysfunction? Acta Anaesthesiol Scand 2005; 49:1225-31. [PMID: 16146456 DOI: 10.1111/j.1399-6576.2005.00791.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
BACKGROUND The pattern of cortisol secretion is influenced by surgery. As cortisol can adversely affect neuronal function, this may be an important factor in the development of post-operative cognitive dysfunction (POCD). We hypothesized that the incidence of POCD would be related to changes in cortisol level. METHODS We studied 187 patients aged over 60 years undergoing major non-cardiac surgery with general or regional anaesthesia. Saliva cortisol levels were measured pre-operatively and at 1 day, 7 days and 3 months post-operatively in the morning (08.00 h) and in the afternoon (16.00 h) using salivettes. Cognitive function was assessed pre-operatively, on day 7 and at 3 months using four neuropsychological tests. POCD was defined as a combined Z score of greater than 1.96. RESULTS After surgery, salivary cortisol concentrations increased significantly. POCD was detected in 18.8% of subjects at 1 week and in 15.2% after 3 months. The pre-operative ratios between the morning and afternoon cortisol concentrations (am/pm ratios) were 2.8 and 2.7 in patients with POCD at 1 week vs. those without POCD at 1 week, respectively. The am/pm ratios decreased significantly post-operatively to 1.9 and 1.6 at 1 week, respectively (P = 0.02 for both). In an analysis considering all am/pm ratios, it was found that the persistent flattening in am/pm ratio was significantly related to POCD at 1 week. CONCLUSION The pattern of diurnal variation in cortisol level was significantly related to POCD. Thus, circadian rhythm disturbance or metabolic endocrine stress could be an important mechanism in the development of cognitive dysfunction after major surgery.
Collapse
|
37
|
Padgett DE, Johnson TW. Zoosporangial discharge in a Protoachlya hypogyna (Saprolegniaceae) isolate from southeastern North Carolina. Mycologia 2004; 96:205-207. [PMID: 21148845] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Inadequate attention to zoosporangial discharge has led to confusion in watermold taxonomic literature. This problem is discussed in light of a specimen of Protoachlya hypogyna that manifests discharge characteristic of three watermold genera, and recommendations are made to reduce future inaccuracies.
Collapse
|
38
|
|
39
|
Johnson TW, Zybailov B, Jones AD, Bittl R, Zech S, Stehlik D, Golbeck JH, Chitnis PR. Recruitment of a foreign quinone into the A1 site of photosystem I. In vivo replacement of plastoquinone-9 by media-supplemented naphthoquinones in phylloquinone biosynthetic pathway mutants of Synechocystis sp. PCC 6803. J Biol Chem 2001; 276:39512-21. [PMID: 11470786 DOI: 10.1074/jbc.m104040200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Interruption of the phylloquinone (PhQ) biosynthetic pathway by interposon mutagenesis of the menA and menB genes in Synechocystis sp. PCC 6803 results in plastoquinone-9 (PQ-9) occupying the A(1) site and functioning in electron transfer from A(0) to the FeS clusters in photosystem (PS) I (Johnson, T. W., Shen, G., Zybailov, B., Kolling, D., Reategui, R., Beauparlant, S., Vassiliev, I. R., Bryant, D. A., Jones, A. D., Golbeck, J. H., and Chitnis, P. R. (2000) J. Biol. Chem. 275, 8523-8530. We report here the isolation of menB26, a strain of the menB mutant that grows in high light by virtue of a higher PS I to PS II ratio. PhQ can be reincorporated into the A(1) site of the menB26 mutant strain by supplementing the growth medium with authentic PhQ. The reincorporation of PhQ also occurs in cells that have been treated with protein synthesis inhibitors, consistent with a displacement of PQ-9 from the A(1) site by mass action. The doubling time of the menB26 mutant cells, but not the menA mutant cells, approaches the wild type when the growth medium is supplemented with naphthoquinone (NQ) derivatives such as 2-CO(2)H-1,4-NQ and 2-CH(3)-1,4-NQ. Since PhQ replaces PQ-9 in the supplemented menB26 mutant cells, but not in the menA mutant cells, the phytyl tail accompanies the incorporation of these quinones into the A(1) site. Studies with menB26 mutant cells and perdeuterated 2-CH(3)-1,4-NQ shows that phytylation occurs at position 3 of the NQ ring because the deuterated 2-methyl group remains intact. Therefore, the specificity of the phytyltransferase enzyme is selective with respect to the group present at ring positions 2 and 3. Supplementing the growth medium of menB26 mutant cells with 1,4-NQ also leads to its incorporation into the A(1) site, but typically without either the phytyl tail or the methyl group. These findings open the possibility of biologically incorporating novel quinones into the A(1) site by supplementing the growth medium of menB26 mutant cells.
Collapse
|
40
|
Johnson TW, Corey EJ. Enantiospecific synthesis of the proposed structure of the antitubercular marine diterpenoid pseudopteroxazole: revision of stereochemistry. J Am Chem Soc 2001; 123:4475-9. [PMID: 11457233 DOI: 10.1021/ja010221k] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An enantiospecific synthesis of structure 1, previously assigned to the antitubercular marine natural product pseudopteroxazole, has been accomplished as outlined in Scheme 1. Coupling of diene acid 3 and amino phenol 4 produced the amide 5, which was subjected to a novel oxidative intramolecular Diels-Alder reaction to generate the tricyclic lactam 6a stereoselectively. This product was transformed via intermediates 7-11 into the diene 13. Cationic cyclization of 13 afforded two diastereomeric tricyclic amphilectanes which were separated and transformed by parallel four-step sequences into 1 and 2, respectively. Neither 1 nor 2 were identical with pseudopteroxazole, indicating a need for revision of the structure, probably to 16.
Collapse
|
41
|
Jung ME, Johnson TW. First total synthesis of xestobergsterol A and active structural analogues of the xestobergsterols. Tetrahedron 2001. [DOI: 10.1016/s0040-4020(00)01086-3] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
42
|
Newton JL, Johnson TW. Detecting digoxin toxicity. Nursing 2000; 30:49. [PMID: 11249434 DOI: 10.1097/00152193-200030120-00016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
43
|
Yellin MW, Johnson TW. A case of Susac syndrome. J Am Acad Audiol 2000; 11:484-8. [PMID: 11057732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
Susac syndrome is a readily recognized but often misdiagnosed disorder almost exclusively affecting women in the 20- to 40-year age range. Characterized by the clinical triad of encephalopathy, branch retinal artery occlusions, and sensorineural hearing loss, patients with Susac syndrome are often misdiagnosed with multiple sclerosis (MS). Unlike MS, however, the disease process extends over a 1- to 2-year period and then goes into remission. This presentation describes the progression of symptoms of a patient eventually diagnosed with Susac syndrome.
Collapse
|
44
|
Mayes BT, Johnson TW, Sadri G. Personality, job level, job stressors, and their interaction as predictors of coping behavior. Psychol Rep 2000; 87:61-81. [PMID: 11026391 DOI: 10.2466/pr0.2000.87.1.61] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Hypotheses concerning the relationships among job stressors, job level, personality, and coping responses were investigated in a sample of 305 electrical contracting employees. Coping behaviors were measured with questionnaire items based on interviews conducted with a sample of the subjects. Neuroticism (N) and Extraversion (E) were the personality variables most strongly related to coping behavior. Overall, more coping variance was explained by personality than by job stressors; however, when the effects of job level and job stressors were combined, they explained more variance in complaining/quitting and seeking social support than did the personality variables. Both work situation and personality seem to be important variables in the choice of coping behaviors. There was no evidence of interactions among personality, stressors, and job level in explaining coping behavior.
Collapse
|
45
|
Lazerwith SE, Johnson TW, Corey EJ. Syntheses and stereochemical revision of pseudopterosin G-J aglycon and helioporin E. Org Lett 2000; 2:2389-92. [PMID: 10930291 DOI: 10.1021/ol006192k] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Revised structures are proposed for pseudopterosin G-J aglycon and helioporin E.
Collapse
|
46
|
Zybailov B, van der Est A, Zech SG, Teutloff C, Johnson TW, Shen G, Bittl R, Stehlik D, Chitnis PR, Golbeck JH. Recruitment of a foreign quinone into the A(1) site of photosystem I. II. Structural and functional characterization of phylloquinone biosynthetic pathway mutants by electron paramagnetic resonance and electron-nuclear double resonance spectroscopy. J Biol Chem 2000; 275:8531-9. [PMID: 10722691 DOI: 10.1074/jbc.275.12.8531] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Electron paramagnetic resonance (EPR) and electron-nuclear double resonance studies of the photosystem (PS) I quinone acceptor, A(1), in phylloquinone biosynthetic pathway mutants are described. Room temperature continuous wave EPR measurements at X-band of whole cells of menA and menB interruption mutants show a transient reduction and oxidation of an organic radical with a g-value and anisotropy characteristic of a quinone. In PS I complexes, the continuous wave EPR spectrum of the photoaccumulated Q(-) radical, measured at Q-band, and the electron spin-polarized transient EPR spectra of the radical pair P700(+) Q(-), measured at X-, Q-, and W-bands, show three prominent features: (i) Q(-) has a larger g-anisotropy than native phylloquinone, (ii) Q(-) does not display the prominent methyl hyperfine couplings attributed to the 2-methyl group of phylloquinone, and (iii) the orientation of Q(-) in the A(1) site as derived from the spin polarization is that of native phylloquinone in the wild type. Electron spin echo modulation experiments on P700(+) Q(-) show that the dipolar coupling in the radical pair is the same as in native PS I, i.e. the distance between P700(+) and Q(-) (25.3 +/- 0.3 A) is the same as between P700(+) and A(1)(-) in the wild type. Pulsed electron-nuclear double resonance studies show two sets of resolved spectral features with nearly axially symmetric hyperfine couplings. They are tentatively assigned to the two methyl groups of the recruited plastoquinone-9, and their difference indicates a strong inequivalence among the two groups when in the A(1) site. These results show that Q (i) functions in accepting an electron from A(0)(-) and in passing the electron forward to the iron-sulfur clusters, (ii) occupies the A(1) site with an orientation similar to that of phylloquinone in the wild type, and (iii) has spectroscopic properties consistent with its identity as plastoquinone-9.
Collapse
|
47
|
Johnson TW, Shen G, Zybailov B, Kolling D, Reategui R, Beauparlant S, Vassiliev IR, Bryant DA, Jones AD, Golbeck JH, Chitnis PR. Recruitment of a foreign quinone into the A(1) site of photosystem I. I. Genetic and physiological characterization of phylloquinone biosynthetic pathway mutants in Synechocystis sp. pcc 6803. J Biol Chem 2000; 275:8523-30. [PMID: 10722690 DOI: 10.1074/jbc.275.12.8523] [Citation(s) in RCA: 108] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Genes encoding enzymes of the biosynthetic pathway leading to phylloquinone, the secondary electron acceptor of photosystem (PS) I, were identified in Synechocystis sp. PCC 6803 by comparison with genes encoding enzymes of the menaquinone biosynthetic pathway in Escherichia coli. Targeted inactivation of the menA and menB genes, which code for phytyl transferase and 1,4-dihydroxy-2-naphthoate synthase, respectively, prevented the synthesis of phylloquinone, thereby confirming the participation of these two gene products in the biosynthetic pathway. The menA and menB mutants grow photoautotrophically under low light conditions (20 microE m(-2) s(-1)), with doubling times twice that of the wild type, but they are unable to grow under high light conditions (120 microE m(-2) s(-1)). The menA and menB mutants grow photoheterotrophically on media supplemented with glucose under low light conditions, with doubling times similar to that of the wild type, but they are unable to grow under high light conditions unless atrazine is present to inhibit PS II activity. The level of active PS II per cell in the menA and menB mutant strains is identical to that of the wild type, but the level of active PS I is about 50-60% that of the wild type as assayed by low temperature fluorescence, P700 photoactivity, and electron transfer rates. PS I complexes isolated from the menA and menB mutant strains contain the full complement of polypeptides, show photoreduction of F(A) and F(B) at 15 K, and support 82-84% of the wild type rate of electron transfer from cytochrome c(6) to flavodoxin. HPLC analyses show high levels of plastoquinone-9 in PS I complexes from the menA and menB mutants but not from the wild type. We propose that in the absence of phylloquinone, PS I recruits plastoquinone-9 into the A(1) site, where it functions as an efficient cofactor in electron transfer from A(0) to the iron-sulfur clusters.
Collapse
|
48
|
Jung ME, Johnson TW. First total synthesis of xestobergsterol A and active structural analogues of the xestobergsterols. Org Lett 1999; 1:1671-4. [PMID: 10836028 DOI: 10.1021/ol991057x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
[formula: see text] A novel pentacyclic polyhydroxylated sterol, xestobergsterol A (1a), has been synthesized in 24 steps and in good overall yield from stigmasterol 17. The key steps of the synthesis are the Breslow remote functionalization of the polyoxygenated steroid derived from 25 and the base-catalyzed epimerization-aldol condensation of the dione derived from 27.
Collapse
|
49
|
Jung ME, Johnson TW. Unusual Cyclization Products Derived from Photolysis of Breslow's Steroidal Benzophenone Esters. J Org Chem 1999. [DOI: 10.1021/jo990800w] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
50
|
Asirvatham SJ, Johnson TW, Oberoi MP, Jackman WM. Prolonged loss of consciousness and elevated porphyrins following propofol administrations. Anesthesiology 1998; 89:1029-31. [PMID: 9778024 DOI: 10.1097/00000542-199810000-00031] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|