chains were generated in the same way as for the isolated a-chains. Thus the model consisted of eight polypeptide chains ( 4 a-chains and 4 13-chains) with the central two a and two 13 chains making up the axial contact interface. The simulations of the above fiber models were carried out without explicit solvent using the GROMOS96 vacuum force field as implemented within the GROMACS suite of programs. Models of HbS mutants were generated using the program SCWRL and the mutant fiber models were generated as for the native HbS model. SCWRL replaces only the side chains of desired residues with the best possible rotamer of the mutated amino acids. Thus the initial backbone conformation of the isolated a-chains and the fiber models remained identical in the native HbS and the mutants. The MD simulation protocol for the fiber models consisted of an initial steepest descent energy minimization for 1000 steps followed by full MD simulation for 1.2ns at 300 K. Essential parameters of the simulation like the radius of gyration, root mean squared deviation from the initial structure as well as the kinetic and potential energies are summarized in Chapter I, Table 4. It was observed that all the global indicators of the simulation stabilized to their average values within 0.2ns. Hence data from 0.2ns till the end of the simulations were used for all subsequent analysis

MD simulations on the a-chain of HbS and the mutants were carried out using the GROMACS suite of programs (Lindahl eta!, 2001). The initial structure of the native protein was taken from the high-resolution x-ray crystal· structure (Harrington et a!, 1997) of HbS (PDB entry: 2HBS). The structures of the mutants were generated interactively using INSIGHT-II. The initial model structures were placed in a simulation box of size 42.8 x 31.5 x 42.7 A. The closest distance from any protein atom to the walls of the box was not less than 9 A. The system was then solvated by adding a bath of SPC (Berendson eta!, 1981) waters in such a way that the density of the system was as close to 1 as possible. The overall charge of the system was neutralized by placing suitable counter ions wherever necessary (Chapter 1, Table 4). The resulting system was then energy minimized for 1000 steps using the steepest descent algorithm. This was followed by 0.3ns of position restrained MD during which the solvent and counter ions were allowed to move freely but the protein atoms were harmonically restrained to their initial positions. Finally, normal MD was run for 3ns using the default GROMACS force field. Bond lengths were restrained to their equilibrium values using the LINCS (Hess et a!, 1997) algorithm and a cut-off radius of 0.9nm was used for non-bonded interaction calculation. The temperature of the system was maintained close to 300K by weak coupling to an external temperature bath with a coupling constant of 0.1 ps. The integration time step used throughout the simulation was 1 fs. MD simulations of single mutant a-chains (K 16Q, E23Q and H20Q) as well as the double mutants (K16Q/H20Q, K16Q/E23Q and H20Q/E23Q) were carried out in a similar fashion for 3ns. In order to directly analyze the effects of the mutations on the contact interface, we also carried out MD simulations on a miniature model of the sickle hemoglobin fiber consisting of a complex of two hemoglobin tetramers. In the low salt crystal structure of deoxyhemoglobin S (Harrington et a!, 1997) the asymmetric unit consists of two HbS tetramers that pack as two strands of HbS molecules running parallel to the crystallographic a axis. Axial contacts occur between two tetramers of the same strand and lateral contacts occur between tetramers of different strands. A canonical fiber model was generated by taking one of the two tetramers in the asymmetric unit together with its neighbor translated along the crystallographic a axis [Figure 7 (A, B)]. Fiber models incorporating mutant a

Strains were streaked on LBON agar plates and after an overnight incubation at 42°C growth was monitored (compared to that on LBON at 30°C as control). Absence of single colony growth was taken to reflect temperature sensitivity. Whenever needed the phenotype was also quantitatively assessed by plating dilutions of cultures on LBON agar plates and the drop in plating efficiency was scored after overnight incubation at 30°C and 42°C

This test was therefore used for two purposes: (i) to distinguish relA+ from relA− strains, and (ii) as a qualitative measure of transcriptional polarity relief at the ilv locus. Growth in the presence of amino acids Serine, Methionine, and Glycine (SMG) was scored on glucose-minimal A plates supplemented with each of the amino acids at 100 μg/ml and compared with the growth on non-supplemented glucose-minimal A plates to score for SMG phenotype

The E. coli relA mutants exhibit SMG-sensitive (SMGS) phenotype i.e. growth-inhibition in the presence of Serine, Methionine and Glycine at 1 mM concentration each (Uzan and Danchin, 1978) and is proposed to be a consequence of transcriptional polarity exerted by a frameshift mutation in the ilvG gene on the expression of downstream genes of the ilvGMEDA operon (Lopes et al., 1989). It was observed in another study that the rho and nusG mutants that are defective for transcription termination conferred SMG-resistant (SMGR) phenotype in a relA1 strain (Harinarayanan and Gowrishankar, 2003)

Lac+ colonies were distinguished from Lac− on MacConkey-lactose plates or on Xgal indicator plates. Xgal is a non-inducing colourless substrate of β-galactosidase enzyme which upon hydrolysis yields dark blue indolyl moieties and hence, the Lac+ colonies on Xgal indicator plates are seen as dark blue colonies. Xgal was prepared as a stock solution of 5 mg/ml in dimethyl formamide and used at a final concentration of 25 μg/ml. On MacConkey-lactose medium (pH around 7.1) on the other hand, Lac+ strains can utilize the lactose sugar present in the medium to lower the pH of the medium to 6.8, resulting in a pink coloured colony while Lac─ strains are unable to utilize lactose to give a white colour

fluorescence by excitation at 440 (pH-independent) and 490 nm (pH-dependent) with emission at 535 nm. Ratio offluorescence intensity at 490 to440 nm was used tocalculatethe vacuolar pH. Background fluorescence was removed by subtracting the fluorescence intensity values of cells without BCECF-AM from the fluorescence intensity values of the probe-loaded cells

Vacuole pH inyeast cells was determined asdescribed previously (Padilla-López and Pearce, 2006). Briefly, log-phase,YPD medium-grown yeast cells were harvested and suspended in 200 μl YPD medium containing 50 μM 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein, acetoxymethyl ester (BCECF-AM; Invitrogen # B1150) to the final cell density of 4 x 107 cells. Cells were incubated at 30 ̊C for 30 min at room temperaturefollowed by three washeswith YPD medium. Washed cells were resuspended in 1 ml YPD medium and 200 μl cell suspension was used for recording

After restriction enzyme digestion, digested products wereresolved on agarose gels and desired DNA fragmentswereextracted from the gel. Concentration of gel-extracted DNA fragments was determined usingspectrophotometerand ligation reactions were set up using a molar ratio of vector to insert of 1:3 and 1:1 for sticky and blunt end ligations, respectively. Ligation mixwas incubatedeither at 22ºC for 4 hor at 16°Cfor 14-16 h. After incubation,T4DNA ligase was inactivatedat 65ºC for 20 min

Genomic mapping of disrupted locusin Tn7insertion mutants was carried out as describedpreviously(Kaur et al., 2004).C. glabratamutants carrying Tn7insertionswere grown in YPD-liquid medium and genomic DNA was isolated fromovernight cultures. 10 μg genomic DNA was digested either with restriction enzyme MfeIor SpeI.Restriction enzyme-digestedDNA was precipitated with 1 ml ethanol and 1/10thvolume of sodiumacetate (3 M,pH 5.2). DNA pellet was washed twice with ice-cold 70% ethanol, air driedand was resuspended in sterilewater. DNA was recircularized with T4 DNA ligase.Resultant circular DNA carriedTn7cassette flanked on bothsidesby the disrupted locus oftheC. glabratagenome. CircularDNA wastransformed in E. coliBW23473 strainwhich contains protein Π (the product of the pirgene) required by R6Kγorifor replication.Twoverified transformants were grown overnight in LB-kanamycin medium and plasmids were extracted. Purified plasmids were sequenced withprimers reading outwards (OgRK 183 and OgRK 184) from both ends ofTn7cassette.Sequences obtained were compared,usingBLAST,against C. glabratagenome sequence database and regionsof Tn7insertions in C. glabratawere mapped

The mixture was then incubated at 37oC for 45 min to radiolabel the oligonucleotide. Simultaneously, the Sephadex G-50 column was prepared in 1 ml syringe. The reaction mixture was loaded on the column and the eluting fractions were collected in the microfuge tube by loading 200 μl milli-Q water on the top of the column. After collecting 5-6 fractions, the tubes were analysed using a GM counter for the amount of radioactivity. The fractions having specific activity between 3.5-4.5 X 106cpm/pmoles were pooled. To this, 100 pM of the complimentary strand of the oligonucleotide was added and heated at 95°C for 5 minutes. The mixture was allowed to annealat room temperature for 1 h and further used in Gel shiftassay

The oligonucleotides of different transcription factors such as NF-B, AP-1, p53 and SP-1 were 5′-end labelled using radioactive γ32-ATP (obtained from BRIT, BARC, Mumbai, India) and Polynucleotide kinase, as per manufacturers’ protocol. The reaction mixture containing the different components, described in the table 2.2below was added in a microfuge tube.Table 2.2: Various components of oligonucleotide labeling reaction mixture

After 14-16 h incubation, hybridization buffer was decanted to a radioactive liquid waste container. Membranes were washed twice with 2X SSC (saline-sodium citrate) containing 0.1% SDS for 15 min at 55°C followed by two washes with 1X SSC containing 0.1% SDS for 15 min at room temperature. Post washes, membranes were rinsed with 1X SSC buffer at room temperature exposed to a phosphorimager screen for 1 h and scanned using a phosphorimager (Fuji Film FLA-9000). The data were analysed by densitometry using Fuji Film Multigauge software V3.11 and graphs were plotted using GraphPad Prism5 software.Note:Depending on signal saturation or non-specificity, high stringency washes were performed starting from 0.5X SSC followed by 0.2X SSC or 0.1X SSC wash buffers containing 0.1% SDSat room temperature

The reactions were carried out at 30 °C for 15 min in 25μlof ubiquitylation reaction buffer (40mM Tris-HCl at pH 7.6, 2mM DTT, 5mM MgCl2, 0.1M NaCl, 2mM ATP) containing the following components: 100μM ubiquitin, 20nM E1 (UBE1), 100nM UbcH5b (all from Boston Biochem). The bacterially purified MBP-WWP2 and MBP-WWP1 E3 ligases were added to the reaction mixture. The bacterially purified and GST bound GST-protein, GST-p73, and GST-ΔNp73 were used as the substrate in the reaction. After the ubiquitylation reaction, the GST beads werewashed five times with 1X NETN buffer and boiled withan equal volume ofSDS-PAGE loading buffer. The ubiquitination of the substrates was determined by western blotting with the substrate-specific antibody

grown culture was inoculated in fresh PS medium with or without 50 μM 2, 2’-dipyridyl and grown at 28°C. At regulartime intervals, 1 ml culture was removed to determine OD at 600 nm. Furthermore, for GUS assay, 1 ml culture was centrifuged to obtain the pellet, which was washed once in sterile miliQ water, and resuspended in 250 μl volume of 1 mM MUG (4-methylumbelliferyl β-D-glucuronide) extraction buffer (50 mM sodium dihydrogen phosphate [pH 7.0], 10 mM EDTA, 0.1% Triton X-100, 0.1% sodium lauryl sarcosine, and 10 mM β-mercaptoethanol),and incubated at 37°C (Jefferson et al., 1987). After appropriate time intervals, 75 μl aliquotes were taken from each reaction mixture, and reaction was terminated by adding 675 μl Na2CO3 (0.2 M). Fluorescence was measured against 4-methyl-umbelliferone as the standard at excitation/emission wavelength of 365/455 nm, respectively. Likewise, GFP activity was measured in Varioscan flash (Thermoscientific) at exitation/emission wavelength of 472/512 nm, respectively by taking 200 μl of culture directly

For reporter assay, GUS and GFP marked Xanthomonas oryzaepv. oryzicolastrains and control strains were grown overnight in PS medium. 0.2

and pelleted down at 1200 rpm for 5 min. The supernatant containing 10% FBS and trypsin were discarded and the cell pellet was resuspended in media containing 1% FBS. 5×104cells suspended in 200 μLDMEM (1% FBS) was added to the upper chamber and carefully transferred to the well of the companion plate containing 700 μLof complete DMEM (10% FBS) to serve as chemotactic agent. Inserts were lifted with sterile forceps and placed in the companion plate by avoiding any bubbles at the bottom surface of the insert. Cells were incubated at 37ºC with 5% CO2for 18 h (MEFs) and 24 h (HeLa and HCT116 cells) to allow migration. At the indicated time, cells on the upper surface of the filter were removed carefully by scrubbing with wet cotton swabs and inserts were dunked twice in excess PBS. Cells that migrated to the lower surface of the filter were rinsed twice with PBS, fixed with 4% paraformaldehyde for 15 min at room temperature. Post fixation inserts were rinsed in PBS twice and air dried at room temperature. Filters were cut carefully through the edges using a scalpel blade and placed inverted on a clean slide so that the migrated cells faced the upward direction. Filters were mounted with vectashield DAPI and covered with a clean coverslip. Migrated cells stained with DAPI were counted by imaging multiple fields using anepifluorescence inverted microscope (Olympus lX51,Image-Pro AMS 6.0 acquisition software, 20x 0.45 N.A. objective).The number of cells migrated to the lower surface was quantified by counting the total number of DAPI positive nuclei in at least 10 random fieldsper sample

Transwell migration assays were conducted as described previously (Raoet al., 2015). Transwell inserts (24 well, 8 μm pore size, Costar, Corning)were used to conduct migration assays. Inserts were equilibrated by adding 1% FBS containing media to the upper chamber, as well as lower chamber of the insert (companion plate) and placed in a 37ºC incubator with 5% CO2till use. Cells were harvested, counted using hemocytometer