Insights into the evolution of extracellular leucine-rich repeats in metazoans with special reference to Toll-like receptor 4

The importance of the widely spread leucine-rich repeat (LRR) motif was studied considering TLRs, the LRR-containingprotein involved in animal immune response. The protein connects intracellular signalling with a chain of molecularinteractions through the presence of LRRs in the ectodomain and TIR in the endodomain. Domain analyses with humanTLR1-9 reported ectodomain with tandem repeats, transmembrane domain and TIR domain. The repeat number variedacross members of TLR and remained characteristic to a particular member. Analysis of gene structure revealed absence ofcodon interruption with TLR3 and TLR4 as exceptions. Extensive study with TLR4 from metazoans confirmed thepresence of 23 LRRs in tandem. Distinct clade formation using coding and amino acid sequence of individual repeatsillustrated independent evolution. Although ectodomain and endodomain exhibited differential selection pressure, withinthe ectodomain, however, the individual repeats displayed positive, negative and neutral selection pressure depending ontheir structural and functional significance.

Isolation and Physico-Chemical Characterization of Extracellular Ligno-Cellulolytic Enzymes of Pleurotus Pulmonarius in Submerged Fermentation.

Pleurotus pulmonarius, a member of oyster mushroom can produced lignocellulosic enzymes laccase, peroxidise and cellulase in liquid potato-dextrose medium in submerged stationary condition. The lignocellulolytic activities were assayed using the extracellular culture filtrate which was partially purified using 0- 80% ammonium sulphate saturation. Different physico-chemical studies were performed using the partially purified culture filtrate. The fungus produced more laccase and peroxidase than the cellulase. The optimum laccase production was found on 17th day whereas cellulase & peroxidase productions were found on 9th& 10th day, respectively. Km of laccase is 4.1mM against guaiacol and 1.25 mM against o-dianisidine whereas Km of peroxidase was 0.72mM and cellulase was 0.06 mM. Optimum pH of laccase was 6.0 but for peroxidase and cellulase it was 7.0. The temperature optima of cellulase (50⁰C) was more than laccase (40⁰C) and peroxidase (30⁰C). All the lignocellulosic enzymes showed a wide range of temperature and pH stabilities. Laccase and peroxidase were fully inhibited by NaCl but it was not so effective against cellulase. P. pulmonarius showed higher ligninolytic (Laccase and peroxidase) activity than cellulolytic (cellulase) activity. The lignocellulosic enzymes isolated from submerged fermentation of P. pulmonarius might be industrially significant as they showed a wide range of temperature and pH stabilities.