Purification and Characterization of Soluble (Cytosolic) and Bound (Cell Wall) Isoforms of Invertases in Barley (Hordeum vulgare) Elongating Stem Tissue

Three different isoforms of invertases have been detected in the developing internodes of barley (Hordeum vulgare). Based on substrate specificities, the isoforms have been identified to be invertases (β-fructosidases EC 3.2.1.26). The soluble (cytosolic) invertase isoform can be purified to apparent homogeneity by diethylaminoethyl cellulose, Concanavalin-A Sepharose, organomercurial Sepharose, and Sephacryl S-300 chromatography. A bound (cell wall) invertase isoform can be released by 1 molar salt and purified further by the same procedures as above except omitting the organo-mercurial Sepharose affinity chromatography step. A third isoform of invertase, which is apparently tightly associated with the cell wall, cannot be isolated yet. The soluble and bound invertase isoforms were purified by factors of 60- and 7-fold, respectively. The native enzymes have an apparent molecular weight of 120 kilodaltons as estimated by gel filtration. They have been identified to be dimers under denaturing and nondenaturing conditions. The soluble enzyme has a pH optimum of 5.5, K_m of 12 millimolar, and a V_max of 80 micromole per minute per milligram of protein compared with cell wall isozyme which has a pH optimum of 4.5, K_m of millimolar, and a V_max of 9 micromole per minute per milligram of protein.     

Length-weight relationship of six demersal fish species from Gulf of Mannar,Bay of Bengal,Eastern Indian Ocean

Length-weight relationship (LWR) parameters were analysed for six demersal finfish species from the Gulf of Mannar coast, Bay of Bengal. Fishes were sampled monthly from the landings of trawlers operated along the coast of Tuticorin and Rameshwaram with a cod-end mesh size of 35 mm at the depth of 60–80 m. Fish specimens were sampled by measuring the total length (TL) and total weight (TW) with precision to 0.1 cm and 0.1 g respectively. The present study also recorded a new maximum total length for Engyprosopon macrolepis, Torquigener brevipinnis and Leiognathus brevirostris.     

Juvenile hormone acid and ecdysteroid together induce competence for metamorphosis of the Verson's gland in Manduca sexta

In the last larval instar of Lepidoptera, ecdysteroid in the absence of juvenile hormone (JH) is believed to cause the shift from larval to pupal development. In Manduca sexta, tissues such as the Verson's gland and crochet epidermis become pupally committed before the earliest pulse of ecdysteroid that occurs on day 2. What causes the change in commitment in these tissues? First it was necessary to determine at what stage these tissues become competent to express the pupal program. Last instar larvae of different ages were induced to molt prematurely by feeding the ecdysteroid analog RH5992 and Verson's gland proteins were analyzed by SDS-polyacrylamide gel electrophoresis. Glands became competent to make pupal proteins between 24 and 32 h after the last larval ecdysis. Next, hormonal regulation of competence was examined in ligated abdomens of 12h last instar larvae. Treatment with JH II acid or methoprene acid plus a low dose (1/50th of the molt inducing dose) of RH5992 induced competence, whereas RH5992 alone, methoprene acid alone or methoprene plus RH5992 did not. Verson's glands maintained in vitro produced pupal proteins in response to methoprene acid together with RH5992 but not with RH5992 alone. Likewise, crochet epidermis lost the ability to make crochets (metamorphic change) only in isolated abdomens treated with JH II acid or methoprene acid and low doses of RH5992. In conclusion, JH acid in the presence of basal levels of ecdysteroid induces tissue competence for metamorphosis. Metamorphic competence is followed by commitment, induced by a small pulse of ecdysteroid in the absence of JH, and finally by expression caused by a high titer of ecdysteroid. It is proposed that JH acid is an essential metamorphic hormone.     

Structure and oligomerization of the PilC type IV pilus biogenesis protein from Thermus thermophilus

Type IV pili are expressed from a wide variety of Gram‐negative bacteria and play a major role in host cell adhesion and bacterial motility. PilC is one of at least a dozen different proteins that are implicated in Type IV pilus assembly in Thermus thermophilus and a member of a conserved family of integral inner membrane proteins which are components of the Type II secretion system (GspF) and the archeal flagellum. PilC/GspF family members contain repeats of a conserved helix‐rich domain of around 100 residues in length. Here, we describe the crystal structure of one of these domains, derived from the N‐terminal domain of Thermus thermophilus PilC. The N‐domain forms a dimer, adopting a six helix bundle structure with an up‐down‐up‐down‐up‐down topology. The monomers are related by a rotation of 170°, followed by a translation along the axis of the final α‐helix of approximately one helical turn. This means that the regions of contact on helices 5 and 6 in each monomer are overlapping, but different. Contact between the two monomers is mediated by a network of hydrophobic residues which are highly conserved in PilC homologs from other Gram‐negative bacteria. Site‐directed mutagenesis of residues at the dimer interface resulted in a change in oligomeric state of PilC from tetramers to dimers, providing evidence that this interface is also found in the intact membrane protein and suggesting that it is important to its function. Proteins 2010. © 2010 Wiley‐Liss, Inc.     

A new alkaline lipase obtained from the metagenome of marine sponge <Emphasis Type="Italic">Ircinia</Emphasis> sp.

Microorganisms associated with marine sponges are potential resources for marine enzymes. In this study, culture-independent metagenomic approach was used to isolate lipases from the complex microbiome of the sponge Ircinia sp. obtained from the South China Sea. A metagenomic library was constructed, containing 6568 clones, and functional screening on 1 % tributyrin agar resulted in the identification of a positive lipase clone (35F4). Following sequence analysis 35F4 clone was found to contain a putative lipase gene lipA. Sequence analysis of the predicted amino acid sequence of LipA revealed that it is a member of subfamily I.1 of lipases, with 63 % amino acid similarity to the lactonizing lipase from Aeromonas veronii (WP_021231793). Based on the predicted secondary structure, LipA was predicted to be an alkaline enzyme by sequence/structure analysis. Heterologous expression of lipA in E. coli BL21 (DE3) was performed and the characterization of the recombinant enzyme LipA showed that it is an alkaline enzyme with high tolerance to organic solvents. The isolated lipase LipA was active in the broad alkaline range, with the highest activity at pH 9.0, and had a high level of stability over a pH range of 7.0–12.0. The activity of LipA was increased in the presence of 5 mM Ca²⁺ and some organic solvents, e.g. methanol, acetone and isopropanol. The optimum temperature for the activity of LipA is 40 °C and the molecular weight of LipA was determined to be ~30 kDa by SDS-PAGE. LipA is an alkaline lipase and shows good tolerance to some organic solvents, which make it of potential utility in the detergent industry and enzyme mediated organic synthesis. The result of this study has broadened the diversity of known lipolytic genes and demonstrated that marine sponges are an important source for new enzymes.     

Engineering and characterization of human manganese superoxide dismutase mutants with high activity and low product inhibition

Human manganese superoxide dismutase is a mitochondrial metalloenzyme that is involved in protecting aerobic organisms against superoxide toxicity, and has been implicated in slowing tumor growth. Unfortunately, this enzyme exhibits strong product inhibition, which limits its potential biomedical applications. Previous efforts to alleviate human manganese superoxide dismutase product inhibition utilized rational protein design and site-directed mutagenesis. These efforts led to variants of human manganese superoxide dismutase at residue 143 with dramatically reduced product inhibition, but also reduced catalytic activity and efficiency. Here, we report the use of a directed evolution approach to engineer two variants of the Q143A human manganese superoxide dismutase mutant enzyme with improved catalytic activity and efficiency. Two separate activity-restoring mutations were found--C140S and N73S--that increase the catalytic efficiency of the parent Q143A human manganese superoxide dismutase enzyme by up to five-fold while maintaining low product inhibition. Interestingly, C140S is a context-dependent mutation, and the C140S-Q143A human manganese superoxide dismutase did not follow Michaelis-Menten kinetics. The re-engineered human manganese superoxide dismutase mutants should be useful for biomedical applications, and our kinetic and structural studies also provide new insights into the structure-function relationships of human manganese superoxide dismutase.     

Associations of <Emphasis Type="Italic">CTLA4</Emphasis> +49 A/G Dimorphism and HLA-DRB1*/DQB1* Alleles With Type 1 Diabetes from South India

The aim of present study was to elucidate the association of CTLA4 +49 A/G and HLA-DRB1*/DQB1* gene polymorphism in south Indian T1DM patients. The patients and controls (n?=?196 each) were enrolled for CTLA4 and HLA-DRB1*/DQB1* genotyping by RFLP/PCR-SSP methods. The increased frequencies of CTLA4 ‘AG’ (OR?=?1.99; p?=?0.001), ‘GG’ (OR?=?3.94; p?=?0.001) genotypes, and ‘G’ allele (OR?=?2.42; p?=?9.26?×?10^?8) were observed in patients. Reduced frequencies of ‘AA’ (OR?=?0.35; p?=?7.19?×?10^?7) and ‘A’ (OR?=?0.41; p?=?9.26?×?10^?8) in patients revealed protective association. Among HLA-DRB1*/DQB1* alleles, DRB1*04 (OR?=?3.29; p?=?1.0?×?10^?5), DRB1*03 (OR?=?2.81; p?=?1.9?×?10^?6), DQB1*02:01 (OR?=?2.93; p?=?1.65?×?10^?5), DQB1*02:02 (OR?=?3.38; p?=?0.0003), and DQB1*03:02 (OR?=?7.72; p?=?0.0003) were in susceptible association. Decreased frequencies of alleles, DRB1*15 (OR?=?0.32; p?=?2.55?×?10^?7), DRB1*10 (OR?=?0.45; p?=?0.002), DQB1*06:01 (OR?=?0.43; p?=?0.0001), and DQB1*05:02 (OR?=?0.28; p?=?2.1?×?10^?4) in patients were suggested protective association. The combination of DRB1*03+AG (OR?=?5.21; p?=?1.4?×?10^?6), DRB1*04+AG (OR?=?2.14; p?=?0.053), DRB1*04+GG (OR?=?5.21; p?=?0.036), DQB1*02:01+AG (OR?=?4.44; p?=?3.6?×?10^?5), DQB1*02:02+AG (OR?=?20.9; p?=?9.5?×?10^?4), and DQB1*02:02+GG (OR?=?4.06; p?=?0.036) revealed susceptible association. However, the combination of DRB1*10+AA (OR?=?0.35; p?=?0.003), DRB1*15+AA (OR?=?0.22; p?=?5.3?×?10^?7), DQB1*05:01+AA (OR?=?0.45; p?=?0.007), DQB1*05:02+AA (OR?=?0.17; p?=?1.7?×?10^?4), DQB1*06:01+AA (OR?=?0.40; p?=?0.002), and DQB1*06:02+AG (OR?=?0.34; p?=?0.001) showed decreased frequency in patients, suggesting protective association. In conclusion, CTLA4/HLA-DR/DQ genotypic combinations revealed strong susceptible/protective association toward T1DM in south India. A female preponderance in disease associations was also documented.