Phenylalanine hydroxylase (PAH), which belongs to the aromatic amino‐acid hydroxylase family, is involved in protein synthesis and pyomelanine production through the hydroxylation of phenylalanine to ...tyrosine. In this study, the crystal structure of PAH from Bacillus cereus ATCC 14579 (BcPAH) with an additional 280 amino acids in the C‐terminal region was determined. The structure of BcPAH consists of three distinct domains: a core domain with two additional inserted α‐helices and two novel auxiliary domains: BcPAH‐AD1 and BcPAH‐AD2. Structural homologues of BcPAH‐AD1 and BcPAH‐AD2 are known to be involved in mRNA regulation and protein–protein interactions, and thus it was speculated that BcPAH might utilize the auxiliary domains for interaction with its partner proteins. Furthermore, phylogenetic tree analysis revealed that the three‐domain PAHs, including BcPAH, are completely distinctive from both conventional prokaryotic PAHs and eukaryotic PAHs. Finally, biochemical studies of BcPAH showed that BcPAH‐AD1 might be important for the structural integrity of the enzyme and that BcPAH‐AD2 is related to enzyme stability and/or activity. Investigations into the intracellular functions of the two auxiliary domains and the relationship between these functions and the activity of PAH are required.
The crystal structure of phenylalanine hydroxylase from Bacillus cereus ATCC 14579 with three distinct domains is reported. The structural features and biochemical properties of the two novel auxiliary domains are investigated.
Acyl-CoA thioesterase is an enzyme that catalyzes the cleavage of thioester bonds and regulates the cellular concentrations of CoASH, fatty acids, and acyl-CoA. In this study, we report the crystal ...structure of acyl-CoA thioesterase from Bacillus cereus ATCC 14579 (BcACT1) complexed with the CoA product. BcACT1 possesses a monomeric structure of a hotdog-fold and forms a hexamer via the trimerization of three dimers. We identified the active site of BcACT1 and revealed that residues Asn23 and Asp38 are crucial for enzyme catalysis, indicating that BcACT1 belongs to the TE6 family. We also propose that BcACT1 might undergo an open-closed conformational change on the acyl-CoA binding pocket upon binding of the acyl-CoA substrate. Interestingly, the BcACT1 variants with dramatically increased activities were obtained during the site-directed mutagenesis experiments to confirm the residues involved in CoA binding. Finally, we found that BcACT1 is not nucleotide-regulated and suggest that the length and shape of the additional α2-helix are crucial in determining a regulation mode by nucleotides.
•Crystal structure of acyl-CoA thioesterase from Bacillus cereus was determined.•BcACT1 undergoes an open-closed conformational change upon substrate binding.•We achieved the BcACT1 variants showing dramatically increased activities.•The additional α2-helix is a key determinant for regulation mode by nucleotide.
The aim of the current study was to biosynthesize the silver nanoparticles (AgNPs) from the bacterial strain of Bacillus cereus (ATCC 14579) extracellularly. When bacterial extract was challenged ...with 1 mM silver nitrate (AgNO3) the color of the extract changed into brown confirms the formation of nanoparticles. These nanoparticles were capped with bovine serum albumin (BSA). UV- visible spectroscopy showed the absorption peak at 420 nm indicates the formation of AgNPs. Fourier Infra –red (FTIR) attenuated total reflection (ATR) spectroscopy showed amide and amine group associated with AgNPs that stabilizes the nanoparticles. Energy dispersive x-ray spectroscopy (EDX) showed a strong peak of silver confirms the presence of silver. Thermo gravimetric analysis (TGA) analysis was used to determine the protein degradation showed less protein degradation at higher temperature confirms the stability of nanoparticles. Transmission electron microscopy (TEM) showed the AgNPs are well dispersed and spherical, and 5.37 nm to 17.19 whereas albumin coated nanoparticles are size ranges from 11.26 nm to 23.85 nm. The anticancer effect of capped AgNPs (cAgNPs) showed the IC50 value against breast cancer MCF-7 at 80 μg/mL, intestinal colon cancer HCT- 116 60 μg/mL, and bone cancer osteosarcoma MG-63 cell line80 μg/mL while against normal fibroblast cells 3T3 cells showed the IC50 value at 140 μg/mL. Lactate dehydrogenase assay (LDH) showed higher toxicity on MCF-7, HCT-116, and MG-63 cells. The apoptotic study clearly showed the blebbing of membrane, chromatin condensation due to the production of reactive oxygen species (ROS) by ethidium bromide and acridine orange dual staining method. The DNA analysis showed the complete fragmentation of the DNA of treated cells when compared with control cells.
Display omitted
•Bacillus cereus was used for the biosynthesis of silver nanoparticles (AgNPs).•AgNPs were capped with bovine serum albumin (cAgNPs).•cAgNPs showed high toxicity towards different cancer cells.•cAgNPs showed high release of lactate dehydrogenase.
