Induction and Analysis of Epithelial to Mesenchymal Transition

Epithelial  to mesenchymal transition (EMT) is essential for proper morphogenesis during  development. Misregulation of this  process has been implicated ...

R&D Systems, Inc.

The genome of the cyanobacterium Synechocystis sp. PCC 6803 contains genes identified as menD and menE, homologs of Escherichia coli genes that code for 2-succinyl-6-hydroxyl-2,4-cyclohexadiene-1-carboxylate (SHCHC) synthase and O-succinylbenzoic acid-CoA ligase in the menaquinone biosynthetic pathway. In cyanobacteria, the product of this pathway is 2-methyl-3-phytyl-1,4-naphthoquinone (phylloquinone), a molecule used exclusively as an electron transfer cofactor in Photosystem (PS) I. The menD(-) and menE(-) strains were generated, and both were found to lack phylloquinone. Hence, no alternative pathways exist in cyanobacteria to produce O-succinylbenzoyl-CoA. Q-band EPR studies of photoaccumulated quinone anion radical and optical kinetic studies of the P700(+) [F(A)/F(B)](-) backreaction indicate that in the mutant strains, plastoquinone-9 functions as the electron transfer cofactor in the A(1) site of PS I. At a light intensity of 40 microE m(-2) s(-1), the menD(-) and menE(-) mutant strains grew photoautotrophically and photoheterotrophically, but with doubling times slower than the wild type. Both of which are sensitive to high light intensities. Low-temperature fluorescence studies show that in the menD(-) and menE(-) mutants, the ratio of PS I to PS II is reduced relative to the wild type. Whole-chain electron transfer rates in the menD(-) and menE(-) mutant cells are correspondingly higher on a chlorophyll basis. The slower growth rate and high-light sensitivity of the menD(-) and menE(-) mutants are therefore attributed to a lower content of PS I per cell.

The menD and menE homologs code for 2-succinyl-6-hydroxyl-2,4-cyclohexadiene-1-carboxylate synthase and O-succinylbenzoic acid-CoA synthase in the phylloquinone biosynthetic pathway of Synechocystis sp. PCC 6803.

Room temperature, light induced (P700(+)-P700) Fourier transform infrared (FTIR) difference spectra have been obtained using photosystem I (PS I) particles from Synechocystis sp. PCC 6803 that are unlabeled, uniformly (2)H labeled, and uniformly (15)N labeled. Spectra were also obtained for PS I particles that had been extensively washed and incubated in D(2)O. Previously, we have found that extensive washing and incubation of PS I samples in D(2)O does not alter the (P700(+)-P700) FTIR difference spectrum, even with approximately 50% proton exchange. This indicates that the P700 binding site is inaccessible to solvent water. Upon uniform (2)H labeling of PS I, however, the (P700(+)-P700) FTIR difference spectra are considerably altered. From spectra obtained using PS I particles grown in D(2)O and H(2)O, a ((1)H-(2)H) isotope edited double difference spectrum was constructed, and it is shown that all difference bands associated with ester/keto carbonyl modes of the chlorophylls of P700 and P700(+) downshift 4-5/1-3 cm(-1) upon (2)H labeling, respectively. It is also shown that the ester and keto carbonyl modes of the chlorophylls of P700 need not be heterogeneously distributed in frequency. Finally, we find no evidence for the presence of a cysteine mode in our difference spectra. The spectrum obtained using (2)H labeled PS I particles indicates that a negative difference band at 1698 cm(-1) is associated with at least two species. The observed (15)N and (2)H induced band shifts strongly support the idea that the two species are the 13(1) keto carbonyl modes of both chlorophylls of P700. We also show that a negative difference band at approximately 1639 cm(-1) is somewhat modified in intensity, but unaltered in frequency, upon (2)H labeling. This indicates that this band is not associated with a strongly hydrogen bonded keto carbonyl mode of one of the chlorophylls of P700.

FTIR difference spectroscopy in combination with isotope labeling for identification of the carbonyl modes of P700 and P700+ in photosystem I.

In photosystem I from plants and cyanobacteria a phylloquinone molecule, called A1, functions as the secondary electron acceptor. In cyanobacteria, genes that encode for proteins involved in phylloquinone biosynthesis can be deleted. Here, we have studied three different gene deletion mutants called menB, menD, and menE mutants. In these mutants, plastoquinone-9 occupies the A1 binding site. Using time-resolved, step-scan FTIR difference spectroscopy we have produced A1(-)/A1 FTIR difference spectra for menB, menD, and menE photosystem I particles at 77 K. These difference spectra show that the P700 triplet state ((3)P700) is formed in a large fraction of the particles. Infrared spectral signatures that are not due to (3)P700 are also observed in the spectra and are suggested to be associated with plastoquinone-9 anion formation in a portion of the particles. By subtracting the known (3)P700 spectral signatures, we produce an A1(-)/A1 FTIR difference spectrum for PS I particles with plastoquinone-9 occupying the binding site. This spectrum shows that a band that we have previously assigned to a C:-O mode of the phylloquinone anion in WT A1(-)/A1 FTIR DS down-shifts approximately 8 cm(-1) when plastoquinone-9 occupies the A1 binding site. Using density functional theory type calculations to produce anion minus neutral infrared difference spectra for both phylloquinone and plastoquinone-9, it is shown that such a downshift is reasonable. A1(-)/A1 FTIR difference spectra, obtained using menB mutant photosystem I particles that were incubated in the presence of phylloquinone, are found to be very similar to those obtained using normal WT photosystem I particles. This result indicates that we were able to reincorporate phylloquinone back into the A1 binding site and that the reincorporated phylloquinone and its immediate protein environment, in both the neutral and anion state, are very similar to that found in wild type photosystem I particles. For the reconstituted menB mutant photosystem I particles, no spectral signatures associated with (3)P700 are observed, indicating that phylloquinone occupies the A1 site in all of the reconstituted menB particles.

Time-resolved FTIR difference spectroscopy for the study of photosystem I particles with plastoquinone-9 occupying the A1 binding site.

Genetic mapping and manipulation: chapter 10--Suppressor mutations.

The elongator (ELP) complex consisting of Elp1-6p has been indicated to play roles in multiple cellular processes. In yeast, the ELP complex has been shown to genetically interact with Uba4p/Urm1p and Kti11-13p for a function in tRNA modification. Through a Caenorhabditis elegans genetic suppressor screen and positional cloning, we discovered that loss-of-function mutations of moc-3 and dph-3, orthologs of the yeast UBA4 and KTI11, respectively, effectively suppress the Multivulva (Muv) phenotype of the lin-1(e1275, R175Opal) mutation. These mutations do not suppress the Muv phenotype caused by other lin-1 alleles or by gain-of-function alleles of ras or raf that act upstream of lin-1. The suppression can also be reverted by RNA interference of lin-1. Furthermore, we showed that dph-3(lf) also suppressed the defect of lin-1(e1275) in promoting the expression of a downstream target (egl-17). These results indicate that suppression by the moc-3 and dph-3 mutations is due to the elevated activity of lin-1(e1275) itself rather than the altered activity of a factor downstream of lin-1. We further showed that loss-of-function mutations of urm-1 and elpc-1-4, the worm counterparts of URM1 and ELP complex components in yeast, also suppressed lin-1(e1275). We also confirmed that moc-3(lf) and dph-3(lf) have defects in tRNA modifications as do the mutants of their yeast orthologs. These results, together with the observation of a likely readthrough product from a lin-1(e1275)::gfp fusion transgene indicate that the aberrant tRNA modification led to failed recognition of a premature stop codon in lin-1(e1275). Our genetic data suggest that the functional interaction of moc-3/urm-1 and dph-3 with the ELP complex is an evolutionarily conserved mechanism involved in tRNA functions that are important for accurate translation.

Allele-specific suppressors of lin-1(R175Opal) identify functions of MOC-3 and DPH-3 in tRNA modification complexes in Caenorhabditis elegans.

Protein phosphorylation is a universal key posttranslational modification that affects the activity and other properties of intracellular proteins. Phosphosite-specific antibodies can be produced as polyclonals or monoclonals in different animal species, and each approach offers its own benefits and disadvantages. The validation of phosphosite-specific antibodies requires multiple techniques and tactics to demonstrate their specificity. These antibodies can be used in arrays, flow cytometry, and imaging platforms. The specificity of phosphosite-specific antibodies is key for their use in proteomics and profiling of disease.

Overview of the generation, validation, and application of phosphosite-specific antibodies.

Trypanothione reductase (TR) is found in the trypanosomatid parasites, where it catalyses the NADPH-dependent reduction of the glutathione analogue, trypanothione, and is a key player in the parasite's defenses against oxidative stress. TR is a promising target for the development of antitrypanosomal drugs; here, we report our synthesis and evaluation of compounds 3-5 as low micromolar Trypanosoma cruzi TR inhibitors. Although 4 and 5 were designed as potential irreversible inhibitors, these compounds, as well as 3, displayed reversible competitive inhibition. Compound 3 proved to be the most potent inhibitor, with a K(i) = 2 ÂµM.

Synthesis and evaluation of substrate analogue inhibitors of trypanothione reductase.

The reduced state of the primary electron acceptor of Photosystem I, A(0), was resolved spectroscopically in its lowest energy Q(y) region for the first time without the addition of chemical reducing agents and without extensive data manipulation. To carry this out, we used the menB mutant of Synechocystis sp. PCC 6803 in which phylloquinone is replaced by plastoquinone-9 in the A(1) sites of Photosystem I. The presence of plastoquinone-9 slows electron transfer from A(0) to A(1), leading to a long-lived A(0)(-) state. This allows its spectral signature to be readily detected in a time-resolved optical pump-probe experiment. The maximum bleaching (A(0)(-) - A(0)) was found to occur at 684 nm with a corresponding extinction coefficient of 43 mM(-1) cm(-1). The data show evidence for an electrochromic shift of an accessory chlorophyll pigment, suggesting that the latter Q(y) absorption band is centered around 682 nm.

Spectral resolution of the primary electron acceptor A0 in Photosystem I.

The chlorosome envelope of Chlorobaculum tepidum contains 10 polypeptides, three of which, CsmI, CsmJ, and CsmX, have an adrenodoxin-like domain harboring a single [2Fe-2S] cluster. Mutants that produced chlorosomes containing two, one, or none of these Fe-S proteins were constructed [Li, H., et al. (2013) Biochemistry 52, preceding paper in this issue ( DOI: 10.1021/bi301454g )]. The electron paramagnetic resonance (EPR) spectra, g values, and line widths of the Fe-S clusters in individual CsmI, CsmJ, and CsmX proteins were obtained from studies with isolated chlorosomes. The Fe-S clusters in these proteins were characterized by EPR and could be differentiated on the basis of their g values and line widths. The EPR spectrum of wild-type chlorosomes could be simulated by a 1:1 admixture of the CsmI and CsmJ spectra. No contribution of CsmX to the EPR spectrum of chlorosomes was observed because of its low abundance. In chlorosomes that contained only CsmI or CsmJ, the midpoint potential of the [2Fe-2S] clusters was -205 or 8 mV, respectively; the midpoint potential of the [2Fe-2S] cluster in CsmX was estimated to be more oxidizing than -180 mV. In wild-type chlorosomes, the midpoint potentials of the [2Fe-2S] clusters were -348 mV for CsmI and 92 mV for CsmJ. The lower potential for CsmI in the presence of CsmJ, and the higher potential for CsmJ in the presence of CsmI, were attributed to interactions that occur when these proteins form complexes in the chlorosome envelope. The redox properties of CsmI and CsmJ are consistent with their proposed participation in the transfer of electrons to and from quenchers of energy transfer in chlorosomes.

Wade Johnson

Stem Cells and Developmental Biology Department

R&D Systems, Inc.

Induction and Analysis of Epithelial to Mesenchymal Transition

Wade Johnson

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Stem Cells and Developmental Biology Department

R&D Systems, Inc.

Induction and Analysis of Epithelial to Mesenchymal Transition

Stem Cells and Developmental Biology Department