ABSTRACT
Laccase is a widely-used environment-friendly copper-containing oxidase found in many plants, insects and fungi. Recently, more and more laccases are also found in bacteria. Myxobacteria are an important bacteria resource. However, myxobacteria are much more difficult to isolate and purify than other bacteria. We used bioinformatic approach to screen myxobacteria proteomes available in NCBI. Based on conserved sequences of four copper binding sites in multicopper oxidase, 30 potential laccase sequences were obtained. Among them, nine genes were synthesized and expressed in Escherichia coli BL21 (DE3). Seven proteins showed laccase activity when tested with traditional laccase substrates. One protein, named rSC-2, was chosen for further research because it exhibited the highest activity towards 2,6-dimethyl phenol (DMP). The molecular weight of rSC-2 was 57 kDa. Its specific activity to DMP was 0.27 U/mg. The optimal temperature and the optimal pH were 60 ℃ and 7.0, respectively. About 50% of the original activity was retained after incubation at 60 ℃ and pH 7.0-8.0 for 1 h. Metals showed different effects on rSC-2. rSC-2 activity was enhanced by several metalsat concentration of 1 mmol/L, such as Ca²⁺ and Mn²⁺. With a higher concentration of 5 mmol/L, the activity of rSC-2 was apparently inhibited. This is the first report of bioinformatics screening myxobacteria laccases in combination with expression in E. coli.
ABSTRACT
Globins are heme proteins that are capable of reversible oxygen binding. All globins can be classified into three families: the M (myoglobin-like), S (sensor) and T (truncated) globins. M and S globins exhibit the canonical 3/3 α-helical fold, and T globins are characterized by a 2/2 α-helical fold. Globins in the genomes of myxobacteria have not been characterized till date. Myxobacteria have very large genomes relative to other bacteria and have a unique life cycle that involves the aggregation of cells into fruiting bodies under starvation conditions. The diversity of globin like sequences in 14 sequenced genomes of myxobacteria is presented in this review. In myxobacterial globins some unusual domain architectures are identified that have not been characterized in bacteria so far; these are: i) a unique chimeric group I 2/2 HbN in the genome of Corallococcus coralloides DSM 2259; ii) M globin chimera harboring a central and a C-terminal globin domain in Sorangium cellulosum ‘so ce 56’ and Plesiocystis pacifica SIR-1 respectively; iii) two tandem globin domains on the same M globin polypeptide in the genomes of Sorangium cellulosum.
ABSTRACT
The chemical structure, biological activity, biosynthesis and application of metabolites of Myxococcus published in literature are summarized in this paper. Emphasis is laid on the actin-binding macrolide rhizopodin, the respiratory chain inhibitors peptide myxothiazol and polyenoid myxalamid, the aromatic compound myxopyronin and saframycin Mx1 acting on nucleic acid, and the macrocyclic compound myxovirescin interfering with cell wall. This review clarifies the diversity of the chemical structure and biological activity of the secondary metabolites of Myxococcus, and provides some clues for the development of their bioactive natural products.