Tissue inhibitor of metalloproteinase-2 (TIMP-2) from red seabream (Pagrus major): Molecular cloning and biochemical characterization of highly expressed recombinant protein

The tissue inhibitor of metalloproteinase-2 (TIMP-2) is originally characterized as an endogenous inhibitor of matrix metalloproteinases (MMPs) to response collagenolysis associated with immune challenge. In this study, the cDNA encoding TIMP-2a gene from red seabream (Pagrus major) muscle was cloned. It was 585 bp encoding a putative protein of 194 amino acids, which comprised all recognized functional domains and showed the high identity to TIMP-2as from other teleost fishes, revealing it belongs to TIMP-2a family. Soluble rTIMP-2a was efficiently expressed using a new constructed pPIC9K-rTIMP-2a vector with high inhibitory activity against to MMP-2 and MMP-9. The recombinant TIMP-2a tagged with 6 histidine residues showed the molecular mass of 23 kDa and isoelectric point of 6.50. Furthermore, the 6 disulfide bonds formed by 12 conserved cysteine residues were identified as functional motifs for its structural stability. In addition, rTIMP-2a possessed the high inhibitory activity against gelatinolytic hydrolysis and degradation of type I collagen which induced by endogenous MMPs in muscle. The results revealed the properties and inhibitory function of rTIMP-2a, which may be a pivotal role in regulation gelatinolytic MMPs metabolization during defense mechanism.

Structural Insights into Substrate Recognition and Activity Regulation of the Key Decarboxylase SbnH in Staphyloferrin B Biosynthesis

Staphyloferrin B is a hydroxycarboxylate siderophore that is crucial for the invasion and virulence of Staphylococcus aureus in mammalian hosts where free iron ions are scarce. The assembly of staphyloferrin B involves four enzymatic steps, in which SbnH, a pyridoxal 5'-phosphate (PLP)-dependent decarboxylase, catalyzes the second step. Here, we report the X-ray crystal structures of S. aureus SbnH (SaSbnH) in complex with PLP, citrate, and the decarboxylation product citryl-diaminoethane (citryl-Dae). The overall structure of SaSbnH resembles those of the previously reported PLP-dependent amino acid decarboxylases, but the active site of SaSbnH showed unique structural features. Structural and mutagenesis analysis revealed that the citryl moiety of the substrate citryl-l-2,3-diaminopropionic acid (citryl-l-Dap) inserts into a narrow groove at the dimer interface of SaSbnH and forms hydrogen bonding interactions with both subunits. In the active site, a conserved lysine residue forms an aldimine linkage with the cofactor PLP, and a phenylalanine residue is essential for accommodating the l-configuration Dap of the substrate. Interestingly, the freestanding citrate molecule was found to bind to SaSbnH in a conformation inverse to that of the citryl group of citryl-Dae and efficiently inhibit SaSbnH. As an intermediate in the tricarboxylic acid (TCA) cycle, citrate is highly abundant in bacterial cells until iron depletion; thus, its inhibition of SaSbnH may serve as an iron-dependent regulatory mechanism in staphyloferrin B biosynthesis.

Effects of endogenous inhibitors on the evolution of antibiotic resistance genes during high solid anaerobic digestion of swine manure

Livestock manure is a reservoir of antibiotic resistance genes (ARGs). The endogenous inhibitors that emerge during high solid anaerobic digestion (HSAD) greatly influence the bioprocess performance and the ARGs. The effect of endogenous inhibitors including volatile fatty acids (VFAs) and free ammonia (FA) on the ARG occurrences during HSAD of swine manure was investigated in this study. The ARG properties during HSAD (8%-14% total solids (TS)) largely differed from the low TS control (4%). The endogenous inhibitors and microbial communities greatly contributed to the three-phase changes in ARGs. The concentrations of VFAs and abundances of Proteobacteria and intI1 were correlated with the changes in ARGs. FA inhibition and VFA accumulation (especially propionate) delayed and restricted the decline of ARGs. The relatively slow rate of changes in ARGs and high ARGs in the end product suggested the high risk of the HSAD digestate for land application.

Elevated Expression of Carboxy-Terminal Modulator Protein (CTMP) Aggravates Brain Ischemic Injury in Diabetic db/db Mice

Deregulation of Akt signaling is important in the brain injuries caused by cerebral ischemia in diabetic animals, and the underlying mechanism is not fully understood. We investigated the role of carboxy-terminal modulator protein (CTMP), an endogenous Akt inhibitor, in brain injury following focal cerebral ischemia in type 2 diabetic db/db mice and their control littermates non-diabetic db/+ mice. db/db mice showed a significant elevation in the expression of CTMP compared to db/+ mice under normal physiological conditions. After ischemia, db/db mice exhibit higher levels of CTMP expression, decreased Akt kinase activity, adverse neurological deficits and cerebral infarction than db/+ mice. To further certain the effectiveness of Akt signaling to the final outcome of cerebral ischemia, the animals were treated with LY294002, an inhibitor of the Akt pathway, which aggravated the ischemic injury in db/+ mice but not in db/db mice. RNA interference-mediated depletion of CTMP were finally applied in db/db mice, which restored Akt activity, improved neurological scores and reduced infarct volume. These results suggest that elevation of CTMP in diabetic mice suppresses Akt activity and ultimately negatively affects the outcome of ischemia. Inhibitors specifically targeting CTMP may be beneficial in the treatment of cerebral ischemia in patients with diabetes.